EB5AGV's Collins 75S-1 restoration

This page is devoted to my recently acquired Collins 75S-1 receiver. Hopefully, I will restore it to a nice working condition as soon as I receive it...

The beginning

After about 10 years without buying Collins gear (here is Spain is _very_ scarce), I have bitten again and have bought a 75S-1. But, checking the fuzzy pictures (yes, it was an eBay auction), it seems it has some uncommon things: it has the Waters Rejection Tuning controls, but also the NB GAIN control (!) and the aspect of the Waters unit is NOT the one I had seen, with the variable capacitor on the front panel but it is on the Rejection Tuning chassis, moved by a pulley and a belt. Also, there is an extra tube shield on the top left area of the chassis and what seems an extra transformer, side by side the standard one. You can see (well, guess!) all of this here:

Any help regarding the extra items will be welcomed!