Well, I'd think Italian. The M being stylized differently makes me wonder if it's not related to a location, Milano? Or maybe the "M" for Motta and "B" for Bergamo?

Clearly a crapload of work went into all the etching/panto stuff, whatever, brain not function. Would appear a spendy bike or passion build. Never seen anything like it but I bet someone else here has! Thanks for sharing.