This is one terrific cable top shape! It is stamped with a logo and the words "Lapp 1934". I don't know much about porcelain, so please correct me if I'm wrong, but I believe this is a U-403B in light brown.

This piece is one of a few interesting porcelain insulators I was lucky enough to have in my possession for just a few days before delivering them to their new owner. I liked them so much, I decided to photograph some of them and post them for reference.