I think it's a judgment call when there is no finish left on the gun. Check with "Thor" who does restoration work on this forum. I doubt that money invested in refinishing would accumulate to it's eventual sales value, but could be wrong on this. Even if you don't plan on selling it because of family connection, there is also the matter of the historical accuracy destroyed when an original gun is refinished.
I do know that there are several people that seek out refinished guns because they look so nice, and have lower prices than more collectible guns.
Jan Still's forum entry at:
http://luger.gunboards.com/showthread.php?t=17906
indicates that the hump was present and not present in 1937.
also transition from rust blued to salt blued that year.
Marc