bristle tuft numbers.
I did not know that the number of tufts varied in the production run, must go and check my prized 541 which I restored seven years ago now. I made mine up from two machines. 541/3 are rare models over here. Wonderful that you have both a good furniture guard and a great original santeen bag. Most were replaced by the regular black bags when the cleaners were taken in for rebuild at hoover at perivale.
Lovely machine, very good job done.
Regards, Walter, Middle of England, UK.