5/8" O/D sounds a bit big for a 1/4" washer, unless that info dates from well before WW2 and hence these are washers to suit the "old" Whit bolt head sizes i.e. before they were reduced by one size relative to each thread diameter?
I don't recall any original fitment BSA washers with a turned chamfer, all that I've encountered from late 30's onward have been to the smaller whitworth size and stamped from sheet, which usually gives them a right way/wrong way to fit them.
Standard size BSA washers (there were plenty of exceptions) I generally replace with Imperial washers to "Table 3 Heavy" spec which are as near as dammit to the NOS BSA washers I have.
Does this sort of washer-counting equate with "rivet counting"?
