Not really what I think of when I think Marshall. The core tone isn't terribly different than Slayer's, though; mid heavy with rounded off lows/highs. This is more gated, though, and sounds like there's a lot of EQ and some compression going on after the preamp, if not after the mic/speaker. Wouldn't surprise me if it was an IR. Boosted 2203 with a gate and 10-band EQ in front, 31-band EQ and compressor in back should get you close.