Here is one I have not seen before. Net two part porcelain lightning arrestor. Embossed:

WESTERN RAILROAD SUPPLY COMPANY TYPE R-2030 LIGHTNING ARRESTOR FOR 10-456 VOLTS

Has two mounting brackets and three wires - two marked L (load) and one marked G (ground). Appears to be just a little earlier than the other one I have listed. Curious why one was labeled a DRY SPOT and this one a Lightning Arrestor. This one is potted and has a cotter pin holding the pieces together.

chocolate brown, shallow chip on base, looks to be dry process! Figure $15 plus actual shipping