Hello David
Rangoon Mounted Rifles is another unit that used a similar sheaf (is it rice though, not wheat?) but they had 'RMR' below the sheaf. Again the South Andaman Volunteer Rifles used a sheaf over 'SAVR'.
I have seen similar buttons to yours, also without any initials, ascribed to various units but I do not believe that they were military.
Wheat sheaves featured on several livery buttons, so that is also a possibility.
Roger
Check out this link for livery buttons with wheat sheaves
https://sites.google.com/site/livery...ied/home/wheat