Sizing tuning machine on old Harmony arch top

[whvick]

Grandkid knocked over the old beater, but I had it out to give them interest in guitars.
They have them on amazon but in sizes
G304, G318, G326 G327
How do I measure it?
Or does anyone know what size Harmony used in 40s and 50s...I am assuming it is at least that old.
Thanks,
whvick

[whvick]

Looks like it is a Harmony Broadway so maybe 1960s
What size tuning machines did it take?
Thanks
Whvick