According to the "Jim Marshall: The Father of Loud" book by Rich Maloof:
"In 1997, 200 virgin 2203 circuit boards were discovered - and used for limited amp run for the Guitar Center chain. Each head bore a plaque with the GC logo, Jim's signature and the legend "1997 LIMITED EDITION JCM800, FINAL PRODUCTION RUN OF MODEL 2203."
They must of had the correct speced transformers of that era too. The problem with the 2203X is cheaper transformers..hence the hum reducing control pot...of which blows up..