OK, I do not want to pull the leading 10sp cog, with integrated spacer, off the Brompton, but I remember it being thicker than the bikegang one. The subsequent cogs have the same thickness in the bikegang set and in a 10sp Shimano cassette. However the spacer for separating the second and third cog that bikegang provided is 2.04mm thick and the 10sp-spacers are about 2.37mm thick. I managed to squeeze 2.55mm or thereabouts onto the Brompton cassette. I went with as wide spacing as was possible for the sake of good shifting, and about equal between the 3 cogs. I have enough pieces in my parts boxes to come up with virtually any spacing I want.

P.S. There is nothing about speed number on the cogs - just letter symbols for cog identification and teeth number.