After world war ii british intelligence -- james bond? -- visited Leica and wrote a complete description in some detail of the manufacturing process underway. It includes a description of how they got that specific finish which, I have to say, I do not think they successfully duplicate today. You can find the whole thing here:
Specifics of the satin finish are:
25. The satin-chrome finish on external metal parts was
obtained by the following process:-
26. Sandblast, hot cleaner without current, cold cleaner
with current, warm rinse, followed by cold rinse, hydrochloric
dip, copper flash, cold rinse, sulphuric dip, cold rinse, bright
nickel-plate, warm rinse, hydrochloric dip, bright chrome,
drag-out rinse, cold rinse, hot rinse, and dry.
27. All articles were jigged on racks and the racks were
screened to obviate side-throw.
28. The bright nickel tank was approximately 6' x 2' x 21/2',
six depolarised anodes being employed. The volt-meter and
ammeter on the resistance control board were all moving
coil pattern and the tank was worked at 2 volts, 25 amps. No
agitation of the electrolite was employed.
29. The chrome tank was approximately 4' x 2' x 21/2', twenty-
eight strip anti-monial lead anodes being employed. Moving
coil volt and ammeters were also fitted in the resistance board
and the tank was worked at 51/2 volts, 300 amps.
30. It was particularly noted that the time allowed for a
satisfactory chrome deposit was exactly three minutes. All the
plating equipment was spotlessly clean.