That is gold, my friend! GOLD!
What a great gift, and what a lovely return to be able to carry on shaving with that lovely razor.
Right - I call that handle a chain mail handle. It will be heavy, as heavy as any from the '30s. It was an alternative style in that era. Later, much later (like the '50s), that handle was reproduced in aluminium and released in a plastic box as a 'Peerless' razor. That's another nice catch, so look out for one of those as a complimentary razor.
Yes, the 1912 patent was retro-applied. All "1912s" were post-1919, after GEM and American Safety Razor merged. Prior to that, GEM had the 'Damaskeene' which was dropped in 1919 and the so-called 1912 released. Prior to 1919, ASR had what we call the 1914. ASR were bigger and absorbed GEM. But that's another history lesson ...
What you've got there is gold! Okay, it's a pretty common combination in that box and with that handle, but less common that the same combination with the chain link handle. It's a great catch, whatever and a great story with it!
Here's mine in a silver tin, possibly '20s:
... and a 'Peerless'
Corrux blades, again
... and my Chain Mail handle in the same case as yours, guessing '30s: