well, I was not able to find 10mm thick - I could have special ordered
17-35-7 but I decided to get it over with and use what I could get - 17mm is
apparently an unusual size

anyway, here is one more hint for anyone so foolish as to take this gearbox
apart

You MUST !!! put the output shaft in place before seating the shaft that
drives it - the bevel gear overlaps over the bearing recess (you don't want
to discover this fact when you have the gearbox all assembled) - so, here is
my new recommended assembly sequence

1. insert the shaft that actuates the gear shifter and get all the shims and
snap rings in place (including the bronze shifting fork) and insert and
tighten studs into front plate
2. insert the shaft that drives the output shaft through its hole in the end
plate and press the bevel gear onto the end, then pull it back as far as you
can without dislodging the gear
3. insert output shaft then put the shaft that drives it back into place and
let the gears mesh
4. place the remaining two shafts near their holes, and put the idler gear
support with the gear on it in place between the three shafts, it rests on
flats milled in two of these shafts
5. drop remaining shafts into proper holes
6. check that everything meshes and seems to work
7. put seal into groove in front plate, drop the pipe that forms the middle
of the housing in place, put seal in groove in back plate and tap the back
plate into position
8. tighten nuts (three nuts, three lockwashers) that hold the whole thing
together
9. put spacer onto shifter shaft, then put cam gear in place, then install
key and mating part onto shifter shaft
10 run shifter shaft to one end, add readout gear and readout (properly
aligned), shifter handle (and tapered pin)
11. insert driven shaft and bearings into rear housing
12 affix covers with oil seals for driven and output shaft
13. affix sheave and key to driven shaft, affix key and output connector to
output shaft
14. install sight glass, drain plug, put the whole mess into the mill,
tighten and fill with oil to proper level.

aaarrrggghhh ----- don't take this thing apart - but if you have one of
these, copy this procedure and save lots of agony