This is a odd one. The 957 cars were 94/95, previous to that time frame, you could order AMG items ala-carte and for model years 92-93, these AMG items would be installed on a new vehicle and the options encoded into the VIN. Prior to 92, this was still possible but the options were not encoded into the VIN, so you would need a invoice to prove these options were installed at the factory.
Also, 957 code vehicles won't have the code 772, as it would be an overlap to code 957. Due to the build of the vehicle the suspect code here is 957, either its a error or like Dave has already mentioned, the car could of been sent back to AMG for a full technology package conversion and the data card was updated. This would be a pretty rare thing to happen but it is possible.
I see a 300TE that has a front end conversion from 94/95, 2000 era wheels, no Gen II AMG body kit, aftermarket exhaust, non factory emblem on the hatch, Sportline option and a manual transmission. The manual transmission is also another odd item, you wouldn't see this on a code 957 vehicle, which might indicate someone did a conversion at some point.
Comes down to the engine though, if it was converted, there should be signs that this was converted, if its a M103, the increase would probably of been to 3.2l and this might be the case due to the 3.2l emblem on the hatch. If its a CIS M104, the displacement would of been 3.4l. You really need to get some pictures of the engine bay to see if there is any evidence of a AMG conversion.