I have an early RK1 head serial # 00249 and I notice that the front panel is different from most of the other RK1 heads that I have seen or come across. The front of mine has the small non vented Mesa Engineering Logo on it and most of what I see has the wide vented front on it.
Are there any...
Every Mark IV I have played pretty much offered up the "goods" right away. You can tweak all nighjt but it's tough to get a bad sound in my experience.