Let me elaborate. The font on the bolt is wrong, and the gas shield shouldn't have 4 digits. It also just "looks" wrong, something you get from seeing a lot of these as I have. The number on the floorplate looks wrong as well, but further than that the electro-etch used was very fragile, when an original gets some patina the number can totally disappear. If an original had that much patina on the floorplate that number would be gone, yet it is very bold. This barreled receiver is a possible combination, but it's odd that the Erma firing proof seems to be ground, but there is a serial number (which is not typical of other SSZZA4 reworked rifles). Most likely it was removed when it was reworked, but the serial added to the receiver is typical of those added upon importation into the US. If it was done at rework, the font would match the barrel. Also, bands should only have 2 digits, and they are also the wrong font.
These reworked SSZZA4 rifles are not common, but follow patterns. Attached is an S/147 reworked RC. Note - serial ground on receiver, but firing proof left intact. Other reworked VZ24 rifles have the same treatment - the only SSZZA4 rifles that retain the original serial are the first reworks from existing rifles, but those do not have a barrel serial number.
There, now the faker can fix the issues with it before it reappears, or the next one. But he better be good, I have tricks up my sleeve to detect them.