questions about Walther GSP

I have a Walther GSP that I know next to nothing about, other than I need a larger grip to use it comfortably. It has a safety, the grip is secured with two screws and there are no letters above the serial number, only 75 and proof marks. I've been advised that I need an attachment dog to be able to use the newer style grips secured with a bottom bolt, but no luck on any information about obtaining one. The gun is absolutely next to new, but the grip is too small to allow me to comfortably fire it. Any help, suggestions and or opinions certainly welcome

I have the older model like yours with the grip attachment screws near the top of the grip.
Rink makes them: https://www.formgriffe.de/en/shpSR.php?sfC=Walther&A=12&p1=400&p2=255
You most likely have the single stage trigger, which in my opinion is the better trigger.
Have fun as they are great pistols.

I bought an adapter and the Walther large grips (blue and tan laminate) from here:  
http://www.carlwalther.com/gsp.htm  

There is another vendor here who can 3D print you larger grips.  I have a set of those also.  
https://www.precisiontargetpistolgrips.com/store/c2/Custom_Grips.html

The above website has lots of parts available.  Champion's Choice used to have some parts.

What rail is that? Thanks