Narrowing Down A Dunhill'a Date

Greetings friends!
I acquired a very lovely Dunhill apple shaped pipe today, and the stampings are all almost gone. There are a few ghosts left though, and I'm thinking with all the clues added together, perhaps we could come to a roundabout timeframe for the creation of this pipe.
Here are all the clues:
>Nomenclature I can make out:
R

Dunhill London

[other side of shank]

MAD....

PAT
>Fishtail Stem
SO, here's as far as I can piece together:
Fishtail stem started in the '30s, as did the Root Briar line I believe.

The Patent number (as of now unreadable) dates this pipe to pre-1954, correct?

So at the moment I'm looking at anywhere from 1930-1954?
I have read that the Group Number system started in 1951, but as of now, I haven't identified any Group Number markings. I'm digging through my stuff looking for a magnifying glass to see if that helps at all.
Do any of you fine folks have any more knowledge? Have I narrowed it down as far as possible at this point? Thanks for the help. I'll update here if I am able to make out any more markings. I think there are a few left to decipher if I look hard enough.
Thanks!
Steve

That's what I'm currently working on, Sable. Hoping I'll be able to make out even just one or two numbers of the patent in order to narrow things down further. Thanks for the info so far!

Excellent! I've located the tops of the shape code, which is 115. Getting closer haha!