L. Bailey 1857 Patent No. 1 Vertical Post
As with most of Bailey's designs, they were simple yet complex for the time and functioned very well. The link will take you to a great article about Bailey's vertical post planes by Paul VanPernis.
This example was probably produced by Bailey sometime during his transition to work for Stanley, perhaps existing in pieces and completed afterwards. Click the link below for additional information on Leonard Bailey and his vertical post planes.
Not wanting copies of his work to escape his control, Leonard was careful to make sure his patent data was predominantly displayed on all his inventions. The practice continued even after he sold his company to the Stanley Brothers.
Note the tension "leaf" spring under the frog to function as counter resistance to the downward pressure and eliminate "slop" on the adjusting screw.
Size number stamped into the back of the lever cap. It also can be found under the frog assembly.
L. Bailey #1 Vertical Post c1857