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.