In my collection I have two block planes from Tower & Lyon (New York, 1884-1916) – Tower & Lyon were a hardware manufacturer which manufactured the planes based on a patent obtained by Orril R. Chaplin in 1872 (No.126,519). Tower & Lyon offered a number of basic models of block plane:
No.0, model makers, L=5″, BW=1-1/8″
No.15, fixed throat, japanned, L=6½”, BW=1-7/8″ (corrugated top, pierced lever cap)
No.18, fixed throat, nickel-plated, L=6½”, BW=1-7/8″
No.20, adj throat, japanned, L=6½”, BW=1-7/8″ (solid lever cap)
No.30, adj throat, nickel-plated, L=6½”, BW=1-7/8″
No.35, adj throat, L=7¼”, BW=2¼” (corrugated top)
In all likelihood, the two planes in my collection are a No.15, and a No.30. The No.15 is unique amongst block planes for having a corrugated deck, i.e. the upper side of the plane body. It is hard to fathom why these corrugations exist. On the sole, corrugations (supposedly) serve the purpose of reducing friction between the planes sole and the wood. Indeed, even the patent described above contains a method of “reducing the area exposed to the pressure of the atmosphere”, by perforating the sole with a series of holes. We’re the corrugations to make the plane more aerodynamic?
The No.15 also has a pierced lever cap, which again serves no real purpose, apart from producing [extremely minimal] aerodynamics, or for decorative purposes. Apart from these design aspects, the No.15 has a fixed throat, and blade depth adjustment mechanism. The No.30 on the other hand has an adjustable throat, and the same depth adjustment mechanism. Its lever cap is solid, and the deck is smooth.
The unique part of these planes is their worm-gear blade adjustment mechanism and support/clasping mechanism. (See article following this).