Is This Right?

[Meridius]

I just purchased what was supposed to be a collector's grade 1915 luger. I posted about it a few days ago. Today, while I had the gun disasembled I noticed that the grips were a different color on the inside and only one had the gun's serial number (77) stamped into the grip. The other grip does not appear to have a serial number. Is this right? If not, does it ruin the luger's value as a collector grade gun? Everything else appears legit. I paid a higher price for a matching gun and I'm trying to figure out if I got what I paid for. Thanks in advance for any advice!