.22 (6mm?) rimfire ID help please

There are many things I know little about, rimfires being one of them ;-) so any help ID’ing this will be appreciated.

Lead bullet, head and lower part of the case is brass and the top half is copper. The headstamp is GG.

OAL is 13.4mm/.526"
Case Length is 7.45mm/.293"
Bullet dia is 5.58/.219"
Rim dia is 7.14mm/.281"

This is a so called doble culotte case,but I don’t know the exact name of your round.The 1926 fiocchi catalog list your round with a conical bullet as " 6 mm Flobert a doppio culotto".I think Jean Pierre will be more helpful than me

Depending of the bullet diameter you can have
Flobert 6 m/m double culot
or 22 double culot

Be carefull about the 6 mm:
you have in the old times different sub families :


The hstp is, undoubtly, GEVELOT.