What am I?

A fair damping this morning at the yard, most of the afternoon while waiting for tradesmen spent editing and faffing while more rain fell. Above a very intricate bit of kit, I have no idea what it was/is for. Your ideas welcome.
The following albums are now available on my Blogspot ....
Burton Constable Hall with WSC
LSM @Middleton Railway
Doncaster Mansion House with WRYS
Take care one and all.