These planes are used to make 5/16" Tongue and Groove match joints on boards 3/4" to 1 1/4" thick, centering on 7/8". Here we have a Type 1.

The
Stanley No. 48 was originally 10 1/2" long. In 1937 it became 8 3/4"
Early types were Black Jappaned. In 1898, the finish changed to Nickel
Plating.
Also, earlier ones had Miller's "Fancy" handle and large brass
headed screws to hold the cutters.
The jappaned planes don't have the Stanley name on them.
This
ingenious plane has a fence which swivels on a pinion. When it is locked
in one position, it will cut a groove. When it is swivelled 180 degrees
and locked in that position, it cuts a tongue. The pivot point on the
fence is offset so that in one position it allows two blades to come
in to use to cut the tongue whilst in the other position, only one blade
is exposed, allowing the cutting of the groove.
This image shows the two blades exposed to cut the groove.
Stanley No. 49
Manufactured 1876 - 1942
Here is a Type 1 No. 49.
It is 10" long. Supplied with two cutters to cut 3/16" tongue and grooves
in 1/2" to 3/4" stock. No difference from the 48 except for length and
the slightly smaller dimensions to take the 3/16" cutter. You can see
also, that the blade holding screws are different from the 48. These
ones are Nickel Plated knurled steel.
Here you can see the Patent Date of July 6 1875.
This Patent Date is on all the Jappaned 48s and 49s.
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This one
is a type 3 from 1911 or later and shows a few changes.
