82Hz

I believe the serial numbers from the late '90s/early '00s used the quarter and year for the three digits after the last slash, so this one probably dates from April-June 2001, which tallies with it having the GP12X pre-amp. The green carpet appeared sometime around 1995, and I have seen serial numbers implying that it was still being used at the end of 2000. I had previously assumed that they continued with it until production ceased under Gibson in early 2002, because I've seen several GP12X heads and combos with the carpet covering (and red stripes, as you say), but yours is the first one I've noticed that deviates. It's interesting, as it has some of the aesthetic of the stuff built in the USA under Peavey ownership around 2008 (the return to the grey vinyl/tolex and the use of gloss black paint for the grille), but with the much nicer-looking (in my opinion) pre-amp. A very smart-looking amp!