Sepia photographs

That is not likely to have an accurate answer. Sepia photographs are still taken (or created in photo editing software) to the present day. Originally, sepia was used extensively as it preserved b&w photos in way that was the most stable of all toned images.

That being said, 1900-1940s sepia images were quite popular. In fact the opening and closing sequences of The Wizard of Oz were sepia toned. Even recently, a few movies of the 70s-90s were also sepia toned (for the effect).

Starting around the late-40s, quite accurate color photos were available for the average photographer, and, as such, sepia were less prevalent but still done. The need to for preserving B&W images became less essential ass the demand for B&W decreased as color images took the forefront.

I think this guy is trying to get les internautes to do his art homework for him.

Frankly I don’t mind. Sometimes knowledge sites like ours serve a helpful purpose when the info is a little arcane or hard to round up..

It also could be spam possibly but it’s a topic about which I have some knowledge. I needed to interrupt my brain surgery practice for just a moment.

I have been out of school for years.

Sometimes folks get suspicious when a lot of questions are asked. It's a bad habit and goes against one of the purposes of this site. Stick around and people will get to know you better.