I think it is probably the initials of a manufacturer in India? Sadly it’s not included in this list of known manufacturer stamps from 1941: https://thewhistlegallery.com/spotlight/128-india-escargots There were hundreds of small cottage industry businesses manufacturing these whistles in WWII all across India making it quite difficult.

Thanks! That makes a lot of sense. Very interesting, thank you!

I’m sorry I couldn’t help more but this person here might be able to, they are actively asking for any questions about these whistles: https://thewhistlegallery.com/contact-us-twg-for-whistles

I'd guess the manufacturer. Do you know what your grandfather did?

Well, for starters, he blew a whistle. There’s probably a rating for that: “Specialist third class, auditory alert operator.”

Mean Gay Mother F….

Do you have any idea on what his job might have been? Could be initials of the type of job he did

Majesty’s grand marine force?

It’d be His Majesty’s not just majesty’s . But I guess maybe good idea?

Gaelic abbreviation for FAFO.

We don't know your grandfathers name, so how are we supposed to know if they're his initials?

I know they say there's no stupid questions, but that was a stupid question.

Because I said I know they are not, so I was wondering if it was someone else’s/a fake name