What can you tell me about the API 2520?

• What made it famous or sot after?
• Did API actually design it?
• This is reissued in this Pulse EQP 1A3. Are they making it? The spec sheets attached have a date of 1981.

I can't just demo one here either. Any history on it would be a fun read at least.

Is this it on the back of this EQP 1A3

Particularity on the Pulse Techniques EQP 1A3 . Not interested in other clones.
I'm addicted to Pultec's this month and want to know how sweet the high-endis on the SS compared to the tube version?

I know you are looking for opinions on these or have some if you are here.