If you email me privately and I will send you a photocopy of either the original DSP 7000 or DSP 7000 M3 manual (I have both). Here is how you can tell what series your 7000 is:
Series 1 - original 20 bit dac, it also has a de-emphasis indicator light
Series II - Burr Brown PCM63 Series K dac
Series III - Pacific Microsonics PND100 HDCD chip, Digital Flywheel. De-emphasis indicator light replaced by HDCD indicator
I also agree with the above post, DSP 7000 Series 3's are excellent candidates for modifications and make an already good dac sound awesome.