I have a 1915 Favorite but mine is blued. I have seen one that was nickel and I think that was an option. I can tell you a little about the gun.
The 1915 was the last, and the best, Favorite. It had a coil spring for the hammer. It should have an octagon barrel. The breech block should be squared off at the rear, not scalloped like the earlier guns. Around 1920, Savage bought out Stevens and started to apply Savage markings, I believe in the form of a logo, "SVG" in a circle, on the left side of the receiver. This makes it easy to tell if your gun was made before or after 1920, Mine is unmarked. There should be a number stamped on the lower tang, under the lever. The action on the 1915s was (IS) slightly beefier and stronger than the earlier rifles. It is sometimes referred as the "Heavy" Favorite.
Ahh...Just found my copy of "Savage and Stevens arms" by Jay Kimmel.
He mentions that several different options could be ordered but then stated that this practice was "generally discontinued" with the 1915 model. He clearly states that records were "Jumbled, and often lost" regarding the Favorite. Rifles might have features that they wouldn't normally have, or that weren't listed in the catalog. If you see no evidence of a refinish that nickel could well be original.
Have you bought the rifle? If the price is good and the rifle is sound, by all means grab it. The are delightful little guns and mine will hit an orange at fifty yards nine times out of ten.
Good shooting.
