Having a 645, I purchased two USA magazines when I bought it and added a couple of Smith magazines later. They function as well as the Smiths. The 10 rounder was an experiment because I was shooting bowling pins at the time (9 pins). The after market and the factory all worked fine.
The gun was a 1st generation auto and as such was solid (heavy, if you choose) not very ergonomic (revolvers had started to be and target autos, well, there was a company that if you made what you wanted on a standard grip using plastic wood they would make you one from scratch).
It is reliable, the Bo mar sights are good. If I run out of cartridges, to paraphrase Bob Smith about his Smith 29, "--- I can always use it as a club." Tell your brother to have fun and shoot well.