Here's an excerpt from Patrick's Blood and Gore site...
http://www.supertool.com/StanleyBG/stan12.htm#num112
#112 Scraper plane, 9"L, 3"W (2 7/8", 1925 on), 4lbs, 1885-1944.
In the humble (hah!) opinion of the author, this is one of the finest tools ever to have been unleashed on the public from New Britain, Connecticut. For the longest time, the plane labored in relative obscurity among a cult of those adroit in the fine points of scraping. It used to be that these things sat unloved at tool events and auctions, and one almost ducked for cover when asking $75 for one. However, a popular scratch n' sniff magazine prominently featured the plane on the cover of an issue, and the prices of the things have never been the same. Everybody wants one, and once you use one, you'll see why. Hey, my life isn't complete without one, and I gotta have one - press here to order.
The tool is nothing but the #12 configured like a #4 smoothing plane. It has the typical rosewood knob and tote like those found on the Bailey bench planes, and it is gripped and pushed just like the bench planes are. Optional cutters could be purchased to turn the plane into a toothing plane; the toothing cutters were available in 22, 28, and 32 teeth per inch. These same cutters also fit the #12.
The earliest model has a bead at the bottom of its front knob. The blades on these first models have the top edge beveled at both corners, probably to spare the workman's hand/knuckles/fingers should his grip ever slip and slam into the blade (this same blade can also be found on the earlier #12's). These blades are not common at all, and they were probably soon dropped in favor of ones with a straight edge along both short dimensions (across the width) of the blade for the reason that some folks like to have both ends of the blade with a burr to be at the ready when one edge goes dull.
The earliest models do not have the number cast into them. They also have the patent date (8/31/58) stamped into the brass adjusting nut closest to the tote. The astute reader will note that the patent date on the nut is nearly some 30 years earlier than the supposed year this plane was introduced. Since the patents expired by the time this plane was offered in the catalog, it seems odd that Stanley would put this nut on the #112. Perhaps they were doing it to intimidate would be copiers, ignorant of patent law, as a warning, but it's more likely that they were just using up old stock since the same nut can be found on the #12's produced during this time. It may be possible that Stanley produced the plane prior to 1885, perhaps 10 years earlier (catalogs and production dates were many times out of synchronization) while the patent was still applicable.
Look at the spewage for the #12 for things that can be damaged on this plane. In addition, check the area of casting, from the sole, where the handle rests. There is a rather fragile extension to the main casting here, which sometimes can be found broken. Never buy one with a high knob of the style found on the bench planes - they only came with the low knob (although some models have a taller than usual low knob that's unique to this plane).
Strangely, many of the earlier planes (say up to WWI) have an unusually thin coat of japanning, making it common for the planes to be found with their finish peeling or blistering. Maybe someone in the #112 department was taking home bottles of japanning to paint the town black?