Grandads old bike !

[Habdzz76]

Can anyone help identify?
As far as I know the photo was taken in the 1920's.
We know he liked Sunbeam motorcycles but I cannot tell which model this is.
There are some clues I have been looking into  - like the  way the exhaust slopes forward is fairly distinctive, and the tank badge is visible but unreadable to me.
Any help or advice appreciated
thanks

  

[L.A.B.]

I think it's a Matchless, similar to, or the same model as this one?: http://www.cybermotorcycle.com/gallery/matchless/Matchless_1928_R-S_250cc.htm

[Habdzz76]

Many thanks for help
From your reply I am convinced the bike is definitely a Matchless now
I had not seen this particular tank badge  - more used to seeing the 'M' with wings emblem, but having looked into this  - it is virtually identical to the attached so I am sure you are correct.
Many thanks for this
I would appreciate any additional info anyone might have on this - many thanks

[33d6]

Its definitely a Matchless RS. The Model R Matchless first appeared for the 1926 season and was Matchless' first 250. It was steadily updated each year and the RS was a "sports" version of the same bike catalogued for the 1928 & 29 seasons. It looks a lot smarter than the original R but the engines are identical. Slowly Matchless developed this engine bringing out an OHV version, the R/3, in 1929, then adding dry sump lubrication in 1930.
This same 250 engine was steadily developed until WWII stopped production in 1940 and by then it was being used in AJS as well.
All prewar Matchless 250 are descended from the Model R but I don't know what year they started using them in AJS.
Cheers,