Ludwll Sibley published the following about L & K: Jack Kaufman left H & K (Heintz & Kaufman) in 1946 to associate with Garrett Lewis and form L & K. Lewis had previously operated the NRTCo. and Lewis Electronics.

They had 11,000 sq. ft. of leased space in Los Gatos but no other plant. They made exclusively small and medium-size glass transmitting tubes of types developed by others, like 4-125As, 250THs, 3C28s, 4E27s, 8020s and maybe 15 more. They did no development work and didn't add types to the line as time went on. They went through hard times in the late '50s; Kaufman left ca. 1956 and apparently so did Lewis. The company went through several reorganizations and finally stopped tube production in May 1962.

Later on (ca. 1964) Marshall Electronics bought the company and apparently made (and rebranded) tubes for a while.
Somebody must've bought rights to the name, just as someone got the H & K "Gammatron" brand and the "Penta" brand, and distributed "somebody's" receiving tubes. The "L & K Ltd." name is part of the transition; the original L & K was incorporated. Ludwell Sibley"