But you are right, there may be more to it. I couldn't find a period American photo magazine on archive.org. There are old issues of a magazine called "Art Photography"[1], which sounds right, but turns out to be more pornography than photography, so I'm not sure it counts (there are only a few ads, for what it's worth).

On the other hand, popular mechanics is on archive.org ([2], featured previously on HN), and it's chock full of ads; the ads vastly outweigh the editorial content. I guess that's a feature, not a bug: in the 80s and 90s my dad bought computer magazines as much for the ads (ie. as a monthly product catalogue) as for the actual content. Like popular mechanics, they were pretty cheap (PM was 35 cents in 1965, around $2.50 in 2017).

The Soviet Photography magazine could serve as a case study. It wouldn't take forever to tally up the amount of ads in each issue, or even a sample of them. The 89/7 issue had zero ads. One of the last available issues is from around '94[3]. There is a bit of advertising, but not a lot.

The final (outer) page is a full page ad for a Canon EOS 1.

[1] https://archive.org/details/ArtPhotography1952Vol03No08 NSFW, obviously

[2] https://archive.org/details/PopularMechanics1960

[3] https://archive.org/details/sovphoto_v1_1994_02

Edit/PS: I expanded my sample size to 3. The second to last page of a 1975 edition[4] has a full page ad for a Practica LTL[5]. No ads, apart from that.

[4] https://ia801505.us.archive.org/10/items/sovphoto_v1_1975_12...

[5] http://camerapedia.wikia.com/wiki/Praktica_LTL I'm sure the advertised 1.8/50 lens made for fun shooting. Better image quality than an iPhone! Both camera and lens fetch ~50 bucks on ebay, today.