Hi the numbers reffered to are stamped on the top of the gearbox.
like a series of center pops. 188 xxxxxx and 141 xxxxx the only part that looks different
is were the upper gear cable lever is. On the 141 There is a opening that looks as if it has a pipe fitted on, and a cover over another opening by the plug in connection, on the 188 there is just a breather.