What's the purpose?
 

While browsing the various threads I keep running into requests for matching serial number parts. Not the whole number, with suffix, but just the last 2 digits, like on firing pins, extractors, etc. I figure, if the poster is successful, they have a weapon with all matching numbers, but they, and successive owners, never know if it's authentic or fabricated. For any given year there may be many s/n ending in 40 for each suffix for instance.

yes, exactly

I don't have an issue with folks trying to 'match' up a part, as every yr they made anywhere from 10,000-180,000 lugers

However, to be correct and 'ok' in my eyes, it would have to be a 'period' piece, same condition, same font, etc. Harder to do than it seems.

I think technically you are making a matching gun, from a mismatch, at least in the luger world. In most gun collecting, M1 Carbine, M1 Garand, 1911's, etc, they were refurbished and parts swapped all the time and it is okay.

TO ME, whats not ok is to 'force match', ie. take a blank part or even worse, a numbered part, number it and call it good.

There is a fine line between trying to semi-restore and fakery.

Is it okay to clean the grips?
Is it ok to re-checker them?
Is it ok to re-straw the golden hue on the correct parts?
Is it ok to take the 'dip' off of a russian dipped luger?
Is it okay to spot reblue one bad spot on a gun?

I have done some of the above, many collectors have done all of the above.

Is it okay to tell the next buyer what you did, what about the next three buyers ? The next buyer after and especially the next will never know. I keep track of numbers of Simson's and it is amazing how a perfectly good gun will change hands in five years...

So, its a personal thing, there are people who are purists and anything messed with on a gun, taints it and it is a 'shooter'...

So it's ok to replace parts, as long as they have the same font, and still maintain the s/n are all matching? It might be worthwhile to collect data of fonts used in certain date ranges. Not that I'm volunteering as I have no collector interest. Now that I've reached senior status I have been acquiring guns of many types that are older than me. All are shooters and I reload and even cast bullets for most.
I guess, if I were a collector, I would always have doubts about these sidearms, unless I had first hand knowledge of origin. For me that would be receiving it from the GI who brought it back.