what's this in my classic gearbox ??

Ok bit of a long story but i changed the auto box and transfer box in my lse last year for supposed low mile bits from another hard dash lse same as mine. I had forgotten until today but when fitting the 'new' bits the wiring loom to the autobox was different and did not have the same engine bay plug as mine so i managed to fit the loom from my existing box, also the transfer box was painted black and had a much shorter handbrake cable than my existing one but fitted just fine anyhow.

Ever since fitting the 'new ' bits i have had 4th gear but torque converter will not lockup... Recently i started having the 'governer syndrome' of no upward gear changes for a few hundred yards in cold weather so i bit the bullet and decided to pull it all to bits again and see what's going on.
pulled tranny box off, govenor out but absolutely spotless in there..
Sump off, i decided to have the control unit out to make sure there was no crud etc inside the auto box and found this oddity you see in the pic!
does anyone have any idea what it is and how to make it work? the servo thing has 2 wires, one i guess to earth inside the box casing and another up to a bodged looking spade connector outside the box. I checked the loom that came with these bits and there are 2 spade connectors that look original and would have connected up this wierd valve.
The date stamp on my control unit is original and dated 9/93, the 'new' one is dated 35/91 ...
Any help much appriciated chaps

if it was on a p38 it would be t/c lock up solenoid but it doesnt look like theres a pressure regulating solenoid on rh side so id think someones fitted the wrong valve to 3.9 block ,cant you swap the one off other block or fit whole unit

thanks James, no there are no other solenoids to be seen anywhere, so am i correct in assuming the odd solenoid is on the t/c lock up valve? seems strange why someone would go to the trouble of welding it on there? The engine that came from the same car was well sorted with lairy cams and big valve heads so maybe they had this setup as some kind of switchable t/c lock up? Guess I'll have to clean up and fit the control valve from my old box but a bit concerned it May leave me with the same shift problems that led to me changing the whole box in the first place ...