Wow! Possibly an original power supply for the IBM 1401 SMS or the IBM 360 System, it is dated November 3, 1966! It is very heavy, about 35 pounds! Very hard to find!! If you have more info to add about this item, please let me know!
I have been told that this was primarily for the IBM 1401, but that parts were also used for the IBM 360 System.
Info from an eBay customer...
I don't see the oil filled resonance capacitor used by the ferroresonant transformer of each power supply of the 1401 in the photos.
This is a 15 volt power supply, the 1401 used 6 volt, 12 volt and maybe a 30 or 48 volt power supplies.
So I doubt it was used in a 1401. The 360, 1130, 1800 or other post 1964 machines using SLT hybrid ICs are much more likely to have used this power supply. Most SLT logic was powered by a 3 volt power supply, but a wide range of other voltages were used for non logic purposes in SLT machines.
The 1620 had one large ferroresonant transformer, so the power supplies in it had an ordinary transformer without the oil filled capacitor (like this) but were 12 volt, 30 volt, 36 volt, 48 volt, and a variable voltage 3 volt supply for margin checking tests. Not a 15 volt supply.
Other pre 1964 machines using SMS cards for logic also generally used 6 volt, 12 volt, 48 volt, etc. supplies. Not a 15 volt supply.