U-290 thru U-299
U-290
similar to a U-290
dry processed
U-290A's these are all dry processed
Just a good look at dry process "crazing"
U-291's
U-291A
I read about this odd marking in an old issue of Crown Jewels (I'll try to add issue info asap) in Jack Tod's articles "Porcelain Insulator News". Mr. Tod said something along the lines of this being an impression of a standard screw head from the manufacturing process.
U-292
U-292A's
U-293's
similar to a U-293B. Love those darker blue specks.
U-294A's
Both are Thomas products.
U-295's
U-295A
U-296
U-297
U-297A's
U-298's
U-299's
If I had to venture a guess I'd say these are all Lapp products except for the yellows which may be Westinghouse products.