I believe both the metal and wood have been refinished. It is impossible to determine which early superposed were made/sold in the first year because FN did not assemble guns based on the serial number on the receiver, but yours is a very early superposed, and probably predates the ad you posted. I have a superposed with a three digit serial number than was assembled/sold in 1933. The twin single triggers tended to be troublesome, and Browning would not repair them after the war, but would convert them to the modern style selective trigger.
Four different triggers were available through most of the 1930's. Double triggers, twin single triggers, a single non-selective trigger (often seen on guns with a skeet configuration), and beginning sometime in the early 30's two varieties of a single selective trigger. The first had the selector button in front of the trigger, and later guns have the selective trigger used on guns sold after the war.
Guns could be purchased by mail directly from Browning, and many variations of grades, barrel length, chokes, stock configuration and other features could be ordered. Browning made a light weight or lightning version, which had a forearm held on by the latch system used on post war guns. The least expensive version of this gun came with no rib at all, but the top of the barrel was matted.
Some very early guns had a monoblock style construction, which yours does not have.
Even though your gun appears to be refinished, it has value to many who collect or accumulate old superposeds, particularly because of the twin single triggers, which have become somewhat difficult to find. You say it has a Browning buttplate. Does it have two large circles superimposed on it, and is it made of horn?