HP7550 Plus plotter, Programming Manual

[inakiz]

Hi.
When HP7550A plotter was released it came along three manual: "Users Guide", "Quick Reference" and "Interfacing and Programming Manual".
Some time after , the "HP7550 Plus" model was released; this plotter was HP-GL2 instead of HP-GL, and had some improvements and a large buffer. The 7550Plus came along two manuals: "Users Guide" and "Computer Information". No "programming" book was included.
Although you can think any HPGL2 reference would do the job, this is not the case because the Plus model has specific commands not found on the HPGL2, and there were some ESC commands not found on the 7550A either.

So my question is: was there a "Programming Manual" specific to the "7550 Plus" (also known as 7550B model) ?