Hi, the last few releases have had some iterations in the handling of \mathchar tokens, but unfortunately it's still broken in 0.89.2, the latex format and core packages such as amsmath and bm really need to be able to interrogate the \meaning of symbols and \meaning on a \mathchar is currently not usable.
\mathchardef\alpha="010B % plain tex definintion \show\alpha \bye produces \alpha=\Umathchar"0"00"00010B. whereas the equivalent \Umathchar should be \alpha=\Umathchar"0"01"00000B. Presumably the internal mathchar to Umathchar conversion is showing fam =0 and appending the fam digits to the character slot? David
