Wow! What great information. Thanks so much.
I never thought I would ever ID those Jamaica, NY precancels, as I couldn't make out any of the letters for certain.
While value may be minimal, most of the precancels were from easily identified sources, except that I was quite curious about the Jamaica, NY precancels as the "Nemo Hygienic Institute" sounded like a rather odd sort of name. I tried to look it up on the internet with limited success, until I came across this newspaper ad from the John G. Myers Co. (Dept. Store?) in Albany, NY dated 1927 ... who would have ever thought that the "Nemo Hygienic Institute" related to Foundation Garments (more specifically,
"To appear uncorseted while being well corseted!")

Just goes to show that stamps need not be valuable to find a interesting story behind them!