IIRC, the original Ruger "Mark" was the "Standard" .22 pistol was their first product, and Bill Ruger did overtly design the grip and grip angle to mimic the (then popular) (corrected below... to Nambu) Luger.
There is more detail in a great book,
Bill Ruger and his Guns
I bought and read the book, and later ended up buying stock in the company (that has done quite well)...
My first pistol was a Mark I, also purchased in the 1970's...
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Igitur si vis pacem, para bellum -
- Therefore if you want peace, prepare for war.