Not really following your logic on the toast forks/Jenks/ Gorham connection, but Rainwater is hardly some "old reference book", and as already mentioned, she cited her source as the Jewelers' Circular. The 'L' is a pound sterling symbol, old versions seen with both single and double cross-bars, have little doubt that Meriden Sterling, La Pierre and Jenks all used this as a nod to the their products being sterling silver...
From the 1904 edition of the Jewelers' Circular Trademark book:
~Cheryl