I have a print with Copyright 1935 Camilla Lucas N Y USA in the upper right hand corner. It has a triangle with SZL in the lower left hand corner. In pencil it is signed Charlot in the lower right hand corner, and in the lower left hand corner it is titled Sur la Piere, also in pencil. Wondering what it is worth, if anything. It is not framed, and there has been some water damage to the matting, but not the picture itself.

One of the best resources that I have found concerning PES is from Google answers, located HERE.
The response from scriptor-ga is very insightful.

Basically PES was set up by Sidney Z. Lucas, hence the SZL mark. He owned a printshop in New York in the years 1940 to 1960 where He
Produced a large number of prints after old etchings.
Generally, prints by Mr. Lucas seem not to reach very high prices.
At the end of the day they look nice, but that's about it.
Most of what is talked about them is from people "boiler rooming" the price on the supposed French history.

I hope this helps.