It's not uncommon to own and shoot guns that are 60 years old, or older.
I'm looking specifically for information on guns that owners would have in their homes or on their person for protection,
Start with literally, anything made by Colt, S&W, and Ruger, ever.... Forget Dirty Harry's .44 Mag, unless the character is both a gun enthusiast AND well funded. Dirty Harry (1971) created a huge demand for the model 29, which had been a slow seller and not very popular before. Such a demand that the factory was running some 2 years behind demand. I knew a fellow who got one in 78 and paid $450 to get it when the retail price was $283.50
Do be sure to consider all the small "cheap" revolvers and those semis considered "Saturday Night Specials". And include heirloom guns.
We're gun people, so we focus on good guns and mostly modern guns, but there are a LOT of people who are technically gun owners who aren't shooters or even enthusiasts. If they have a pistol in the house, it's not likely to be something new, its probably something that has been in the family for a while, and is kept "just in case". There were quite a few older model Colts, & S&Ws, but also a LOT of Iver Johnson and H&R top break revolvers often nickeled, in obsolete .32 & .38 calibers, kept in a shoe box on a closet shelf. Also all the foreign made copies of them, which were freely imported in huge numbers until 1968.
No Glocks, until the later 80s, and even then they were uncommon among most "gunowners". It wasn't until after Glock conquered the police market that civilian ownership began to increase, and it took some years before it was really widespread.
Also, don't ignore the possibility of a black powder pistol. The Civil War Centennial created a lot of popularity for cap & ball replicas, and not being "legally" firearms under Fed law could be mailed direct. Finished guns and lots of kits were out there in the 70s and 80s, and while people didn't carry them for protection, or usually depend on them for that, your cop character(s) might easily run across one or more in someone's house.