These are German EQ modules from the 1950/60's , some call them the German Pultec
Huge tone from the trio of transformers inside each one

Since these are passive modules they where usually followed by V72's for 34 dB of make up gain in the Old Days
but any decent suitable line amplifier can be used for this, API , CAPI, NEVE, etc .

In fully working Condition and sounding Glorious