Help to identify these unusual markings.

[CutlassCollector]

Hi can anyone help identify these markings.

There are two stamps an M surmounted by a crown and a B surmounted by a crown, both in ovals. These probably indicate that the axe was made in France but for which country?
There is a large crown with initials below and a grappling hook possibly signifying a navy.

The markings are on the top of a boarding axe.

Any thoughts greatly appreciated.
Regards, CC.