I have a US Odeon recorded in Europe by Enzo Baccante. It's opera.
The matrix numbers are XM 1805 and XM 1806. It's a 10-1/2" disc.
What record company used this prefix? It's not Fonotipia who used XPh. I
assume it's Odeon. The " X" prefix was used by Odeon for 10-1/2" discs and
the next letter was usually an abbreviation for the city in which it was
recorded or some other guide to its geographical origins.
Where woyld "M" be, then? Milan was Fono's turf. Malta? Malmo? Munich?
I've plenty of ideas but real knowledge would help.