That sheath is definitely a Heiser-Randall west stamp, made between 1959 and 1963. This is what Joe is calling "HKL" which stands for Heiser-Keyston-Lichtenberger the corporate name for Heiser after the company was bought in 1959.
We speculated that the corporate stamp for Heiser-Keyston-Lichtenberger was so cartoonish that Mr. Randall finally made them use a stamp of his own. This is a reasonable assumption given the unacceptability of the HKL corporate stamp (you can see it about page 8 of Magic Randall line).
Note that "HKL" does not denote a new or separate company. The same Heiser people were making the sheaths in the same way in the same factory both before and after the Randall Stamp replaced the Heiser one. However, "HKL" can be a convenient shorthand way to refer to a Heiser-made sheath, with west or center facing Randall stamp, center retaining snap, etc.
examples: Heiser-Keyston-Lichtenberger corporate stamps of 1960
