Here is one of those glass cups or jars that you often find. Anybody know what these are from? My guess is that they were sold full of something (like jam maybe??) and then people used them as cups.
I think your right Bob = jelly jar/drinking glass. They still make them (not exactly the same as yours) We still have a few around here from when the kids were little.
River was a murky 48 degrees this am. Warmed to 50 by noon. Almost zero current as the water is way low.