3 spline snap ring cogs often followed the Sturmey Archer AW3 pattern.
in 13 - 21t most 1/8" thick..
[ FWIW, Sachs made a short cassette for hubs they supplied to Brompton
with 2 3/32"Thk cogs, 13/15.. the 15t on those, 3 short gate teeth
Fit AW3 hubs, I put 1 on my BSR Brommie.. ]