Good Morning Kathleen,
That is quite a find. All of the floats with marks that you detailed are American-made floats. The Cincotta Brothers floats were from Cincotta Brothers Hardware & Supplies in San Francisco. They were machine-made, which leads me to the thought that they were made for Cincotta Brothers by Owens/Illinois Glass Co. of Oakland, Ca., which as you know, is right across the bridge from San Francisco. They are not a rare float, but are not common either. Made in clear glass, they are offered for sale on Ebay auctions about 6 times per year, give or take a few. I do think that it is very interesting that you have three roped together. Without seeing a photograph of them, I do not know if they were roped together to act as a net marker.
The other NW marked floats are also American machine-made glass balls. They were made by Northwestern Glass Company of Seattle, Washington. I would like to know what the diameter of the floats are. You can make an easy measurement by just using a ruler to measure the height from top to bottom. That is a rough diameter, but tells me all that I need to know. These floats were made in three sizes that I know of. The largest is approx. 6 inch diameter. They were made in clear and beer bottle brown glass, but also occur in a nice honey yellow glass, and sometimes very dark brown.
All of these floats were made during the 1940's, especially during the WWII years, when there was a demand for fish to supply the homefront with protein and vitamins, as well as the troops. The North American fishermen had no access to German or Japanese-made glass floats, so there was a demand which was quickly filled by a few American Glass Companies. The Northwestern Glass Co. made more floats than any of the others involved, and their floats, except for some very rare test models, are common.
I am interested in the float that you say may be yellowish glass with a mark. Too bad that you have not been able to post your drawing or a photo. I see that Cathy B has offered you help, and hope that you can post the mark. Do let the readers know more about that float including it's diameter.
Thank you for your post.