This is a really nice condition Banker. The case is 10KT yellow gold plate with a stainless steel back and M6 date code. The dial is a real beauty with a sunburst center and engraved hour markers. The movement is a 11AL 17 jewels with a M5 date code. The case dial combination I could not find an ad match. The case is Banker G while the dial is seen on the Banker K. I believe this to be a factory combination and most likely a variant of the Banker. Possibly a previously undocumented Banker J?
Tough call, normally with a possible swapped dial (movement) we lean toward the case ID but I could not classify this as a G. I might be OK tagging it as a Banker noting a dial combination previously undocumented. Short of a line book entry I would not classify as 'factory'.