PEPCO, a lot of their clamshells have Photocell sockets....mostly the GEs! Frederick MD, clamshells some has PC sockets but short cap is used on them instead......seems they may have gotten refurbished or used clamshells from other places which makes sense as you see varity of clamshells in one road!
Yeah that was a great find. This is the first clamshell I have ever seen in CA with a PC socket. I did see an OV20 with a PC socket by US 44 in Rhode Island though.