Hi Glen,
I am not sure if it is an east or west coast spec, at the moment it has a rgs or catalina tank on.
Have joined the BSA owners club - so will be requesting a dating certificate asap.
It has the full valanced chrome mudguards which are in remarkably good condition, serial numbers seem correct for a 61 SR, the hand painted in yellow "made in England " is still visible below the headstock.
I have budget another 4K for the restoration.