Lee

The earliest K-frame, from 1899 through maybe 1905 or so, had a different
rear-sigt blade. The blade itself was much thinner than this example, and
the bottom is a bead, instead of those two angles corners. The rear sight
base itself was different, as well. In your later example, the blade does not
slide through, from one side to the other, but rather lifts out. In the
early rear sights, the rear base has a thin cut, and then a hole that traverses
from one side to the other. The blade does not lift out, but rather slides all
the way through, from one side to the other. Like this sight, there are two
small screws, but they are flat on the ends, instead of being pointed.

Another difference is that, on these very early bead-based blades, the blade
itself is numbered to the gun. Typically its the last three digits of the
serial number, but sometimes its the last three digits of the assembly number.

A final difference is that these very early target front sight blades were
typically either a Paine bead, or a knife-like blade. Both of these are very
thin, with the result that the notch in the rear sight blade is also very very
tiny. The introduction of the Patridge front sight blade, which is a much wider
blade than the Paine or knive-edge, required a much wider rear sight notch.

Regards, Mike Priwer