9A New redshift determined for this source, formerly known as 9A Zamorani et al. (1999A&A...346..731Z) X043-12. 15A Object 15A is not regarded as the optical counterpart, since the 15A identification of the line features is uncertain and the positional offset 15A is rather large. A very faint object at the detection limit lies in the 15A X-ray error circle. A lower limit of f_X_/f_opt_~65 for this source was 15A estimated by assuming a limiting magnitude of R=24. 17A Source 17 is a likely X-ray blend with large contrast between the two 17A individual sources. Object 17A is a unique identification of the brighter 17A X-ray source, whose X-ray flux is likely to be overestimated due to 17A blending. 20A & 20B: Zamorani et al. (1999A&A...346..731Z) identified source 20 with the 20A M star 20B. Some contribution of the M star's X-ray flux cannot be 20A excluded, but the identification with the type II AGN (object 20A) seems 20A more likely, since the X-ray colours indicate a relatively hard spectrum. 20B & 20A: Zamorani et al. (1999A&A...346..731Z) identified source 20 with the 20B M star 20B. Some contribution of the M star's X-ray flux cannot be 20B excluded, but the identification with the type II AGN (object 20A) seems 20B more likely, since the X-ray colours indicate a relatively hard spectrum. 22A & 22B: X-ray source 22 is a probable blend. Objects 22A and 22B fall on top 22A of the two suspected point sources. We regard both optical objects as 22A likely counterparts of the X-ray blend and distribute the measured X-ray 22A flux evenly between the two sources. 22B & 22A: X-ray source 22 is a probable blend. Objects 22A and 22B fall on 22B top of the two suspected point sources. We regard both optical objects as 22B likely counterparts of the X-ray blend and distribute the measured X-ray 22B flux evenly between the two sources. 26A New redshift determined for this source, formerly known as Zamorani et al. 26A (1999A&A...346..731Z) X301-29. 32A NV strongest emission line in the spectrum (brighter than Ly-alpha). Narrow 32A emission lines are present and the object is classified as 'N' (narrow 32A emission line galaxy). However, all narrow emission lines have underlying 32A broad components. Therefore, the classification flag is set to '0'. 35A & 35B: Two galaxies at equal redshift, the brighter galaxy 35A is regarded 35A as the X-ray counterpart. The possibility that the X-ray source is a 35A galaxy cluster cannot completely excluded, but an X-ray extent is not 35A obvious. For 35A a new redshift is determined (update to Zamorani et al. 35A (1999A&A...346..731Z) X022-48). 35B & 35A: Two galaxies at equal redshift, the brighter galaxy 35A is regarded 35B as the X-ray counterpart. The possibility that the X-ray source is a 35B galaxy cluster cannot completely excluded, but an X-ray extent is not 35B obvious. For 35A a new redshift is determined (update to Zamorani et al. 35B (1999A&A...346..731Z) X022-48). 42A New redshift determined for this source, formerly known as Zamorani et al. 42A (1999A&A...346..731Z) X031-24. 46A X-ray blend with major contribution from the southwestern component with 46A type I AGN 46A as counterpart. 47A & 47B: Two narrow emission line galaxies at equal redshift. The possibility 47A that the X-ray source is a galaxy cluster cannot completely excluded, but 47A an X-ray extent is not obvious. 47A is assumed to be the optical 47A counterpart. 47B & 47A: Two narrow emission line galaxies at equal redshift. The possibility 47B that the X-ray source is a galaxy cluster cannot completely excluded, but 47B an X-ray extent is not obvious. 47A is assumed to be the optical 47B counterpart. 63A Unresolved narrow emission lines are present and the object is classified 63A as 'N' (narrow emission line galaxy). However, the CIV emission line has 63A an underlying broad component. Therefore, the classification flag is set 63A to '0'. 66A The identification is not unique, since the optical image reveals a 66A possible second object inside the 1sigma-X-ray position error circle. 133A Narrow emission lines are present. The object is classified as 'N' (narrow 133A emission line galaxy). However, Ly-alpha shows a resolved, broad base. 133A Therefore, the classification flag is set '0'. 137A Broad absorption line quasar. 151A Probably a spurious detection of the X-ray source. The source is kept in 151A the source list for the formal reason of having an ML=5.2, but is not 151A considered further. 191A Optical spectrum in Zitelli et al. (1992MNRAS.256..349Z) indicates a type I 191A AGN with typical broad emission lines. However, this object shows the 191A lowest X-ray-to-optical flux ratio of all AGN in our sample. 191A f_X_/f_opt_=0.04 suggests an X-ray faint AGN. Since this object was not 191A detected by ROSAT, it is unlikely that the extreme f_X_/f_opt_-ratio is 191A due to a temporary low X-ray state of the object. Furthermore, it is one 191A of the type I objects with intrinsic absorption 191A (N_H_=(5.75_-2.81_^+3.83^)x10^22^cm^-2^). 217A & 217B: X-ray blend, the identification of 217A with the southeastern 217A component seems unambiguous, the identification of 217B with the 217A northwestern component is not unique, since a similarly bright, close-by, 217A but still unidentified object is present at the same distance from the 217A X-ray source. 217B & 217A: X-ray blend, the identification of 217A with the southeastern 217B component seems unambiguous, the identification of 217B with the 217B northwestern component is not unique, since a similarly bright, close-by, 217B but still unidentified object is present at the same distance from the 217B X-ray source. 224A & 224B: Two galaxies at equal redshift, no obvious X-ray extent. 224B & 224A: Two galaxies at equal redshift, no obvious X-ray extent. 253A & 253B: Two objects at similar redshift with 2 mag difference in the 253A optical. The brighter object 253A is regarded as the identification. 253B & 253A: Two objects at similar redshift with 2 mag difference in the 253B optical. The brighter object 253A is regarded as the identification. 280A Object is classified as 'B' since CIII is well resolved with 280A {Delta}lambda~72{AA} (FWHM). Ly-alpha and CIV are narrow emision lines, 280A but show strong absorption with broad underlying components. The 280A classification flag is set '0'. Possible broad absorption line quasar. 315A & 315B: As counterpart candidates for X-ray source 315, an M star (315A) 315A and a NELG (315B) are found. The hardness ratios of 315 indicated an 315A obscured X-ray object. Therefore, we regarded 315B as the identification. 315B & 315A: As counterpart candidates for X-ray source 315, an M star (315A) 315B and a NELG (315B) are found. The hardness ratios of 315 indicated an 315B obscured X-ray object. Therefore, we regarded 315B as the identification. 361A Broad absorption line quasar. 382A & 496A: Physical quasar pair, separated by 17 arcsec, at z=1.904, 382A d_A_=143kpc. The spectra are different, i.e., the two objects are not 382A lensed images of the same source. 496A & 382A: Physical quasar pair, separated by 17 arcsec, at z=1.904, 496A d_A_=143kpc. The spectra are different, i.e., the two objects are not 496A lensed images of the same source. 437A Spectrum, optical, and X-ray image, and relative soft hardness ratios point 437A undoubtedly to an M star as X-ray source. However, a flux ratio 437A f_X_/f_opt_=1.7 is unusually high for an M star as the X-ray 437A identification. 512A & 512B: Zamorani et al. (1999A&A...346..731Z) identify the NELG 512B with 512A the X-ray source. The 2mag fainter NELG 512A lies somewhat closer to the 512A X-ray position. While both galaxies may contribute to the observed X-ray 512A flux, we assume object 512A as the counterpart in the following. 512B & 512A: Zamorani et al. (1999A&A...346..731Z) identify the NELG 512B with 512B the X-ray source. The 2mag fainter NELG 512A lies somewhat closer to the 512B X-ray position. While both galaxies may contribute to the observed X-ray 512B flux, we assume object 512A as the counterpart in the following. 582A Spectrum, optical, and X-ray image, and relative soft hardness ratios point 582A undoubtedly to an M star as X-ray source. However, a flux ratio 582A f_X_/f_opt_=1.5 is unusually high for an M star as the X-ray 582A identification. 607A & 653A: Detected as a single X-ray source by ROSAT Zamorani et al. 607A (1999A&A...346..731Z) X404-23, X-ray source 653 is brighter and closer 607A to X404-23 and, therefore, treated as the detected ROSAT X-ray source. 607A The broad spectral feature at 7100{AA} in the optical spectrum of 607A is 607A spurious due to the zeroth order light of the neighbouring slit. 653A & 607A: Detected as a single X-ray source by ROSAT Zamorani et al. 653A (1999A&A...346..731Z) X404-23, X-ray source 653 is brighter and closer to 653A X404-23 and, therefore, treated as the detected ROSAT X-ray source. The 653A broad spectral feature at 7100{AA} in the optical spectrum of 607A is 653A spurious due to the zeroth order light of the neighbouring slit. 615A & 615B: Both objects, the broad emission line object 615A and the narrow 615A emission line object 615B, are possible counterparts to the X-ray source. 615A We regard the fainter, but positionally better matching object 615A as the 615A counterpart. 615B & 615A: Both objects, the broad emission line object 615A and the narrow 615B emission line object 615B, are possible counterparts to the X-ray source. 615B We regard the fainter, but positionally better matching object 615A as the 615B counterpart. 632A Spectrum suggests a BL-Lac object, but the object is not a radio source, 632A classification unclear.