This is a revered  Vintage Urei 1176 Blackface, Rev D … please do not think all the vintage blackface 1176’s were created equal … that is far from the truth!
The Rev D is arguably the best bass compressor on the planet!  It has the fuzzy distortion and the hugeness that is famous in the very early 1176 revisions.
The D, is 2 revisions away from the revered 1176 Blue Stripe (rev B), and what a lot of very knowledgable folks may not realize is that it is according to MIX MAGIZINE’S article on the  "1176 Revision History”,  the “D” is similar to the same circuit as the “Blue Stripe, Rev B”.
READ BELOW … this is straight from the article.
Rev B (November 1967 to January 1970, serial numbers 217-1078) includes an all bipolar design to replace the FET-based circuit in the signal preamp section. A tap off the emitter of the first transistor of this stage provides feedback back to the FET gain reduction stage.

Rev C (January 9, 1970, serial numbers 1079-1238) introduces the first of the black-face models and the LN suffix, which stands for low noise. An additional circuit designed by Brad Plunkett (and epoxy-encapsulated to keep it secret, pending a patent filing) reduces the drain-to-source voltage on the gain-reduction FET to keep it within its linear range designation. The LN circuit epoxied module and the Q-bias pot are soldered and mounted directly onto a Rev B circuit board.

Rev D (into 1973, serial numbers 1239-2331) has no circuit changes but features a redesigned main printed circuit board incorporating the LN circuitry and Q-bias pot.

I have owned a Blue Stripe, Rev B and I currently have two Blackface Rev D’s, and they do sound similar but certainly not the same … Actually I have both Rev D’s calibrated by Vintage King to be as close as possible in sound (I use them often on room sounds for drums, vocals, etc.) and these two units really don’t sound the same either … They are similar in sonic characteristics and work great together, but they are certainly not identical. These old Vintage Comps all have a personality of their own, but they have a TON OF MOJO!
In closing, The REV D (I have two to sell, the other is not listed yet) is an unbelievable compressor!  I have found it to be more useful on a lot more things that the Blue Stripe, but I will honestly tell you that if you have a male singer that has any edge to their voice the Blue Stripe Rev B, is the go to comp 100% of the time!  It is not beatable by anything!  
The REV D is the next best thing, way more useful, and even though very expensive a bargain at the price!
If you have any questions, give me a shout.