I purchased this 'Golden' calculator in Japan (via a good friend) from an antique dealer who did not know (or would not tell) its history.
It's possible that some enterprising individual stripped the paint from this piece, however, I suspect it was originally finished in all brass as shown, because even the sliders and screws appear to be of brass, which is unusual as far as I can tell. (If you have any information about this, I'd be interested to hear from you! Send me a note)
I have seen examples where the top plate is brass while the carriage and the rest below remains painted, and these two-tone machines are also quite beautiful. Here is an example from the same era:
Here you can see that though the top plate has been stripped of paint, the screws do not appear to be made of brass as with the 'Golden' model.
Original Odhner is one famous brand of a great many that produced this 'pinwheel' style of machine (so-called because a set of pins project from the large central drum, which rotates as the crank is turned). Willgodt T. Odhner invented the design in 1874 in St. Petersburg (though the American inventor Frank Baldwin independently originated a very similar concept two years earlier).
And how to operate the calculator for multiplication division etc.: