Your father's version looks better, and as you noted he made it and the gauntlet has been thrown.
Back in the '90's a processing equipment manufacturer I was buying a boatload of equipment from gave me a box of these that were molded out of FRP with a metal tab inserted to pry under the cap; they also had a slot on the "back" to help pry up tabs on cans (they were changing their logo and wanted to get rid of them):
I was traveling a lot in those days, and passed them out to happy flight attendants (no more broken nails).
My plastic one is shaped slightly differently so can't get the bottle "lifter" under a tab (but if you flip it over you can make it work on a tab, just not as easy as the slot).So I have been giving this some thought... since I am making it out of stainless steel... I was concerned with the tab on top (for the can opener) to be a safety risk...
Turns out, this design also works with cans... here, take a look (and yes, I need some hand lotion for my dry hands , shut up! )..
View attachment 424741
I should have enough material to try both... will try to make both designs and see if I can make the top one not be a risk for cutting myself with it...