No sweat, clb. Dockside is the general chit-chat area. While you got some replies, the Boat Topics section has a wider audience, so it's just a better place to ask.
Well after cleaning the grunge off the first pic is is a scott plastics corp.
The base (on boat) does not attach, I've not used one in a coons age' are the slider base ( has the white lock key) offered in different sizes?
The website did not help much.