La Creuset a Dansk Ware have only done the enameled ones for ever. I have the "Red and Blue" books that show all the info and collectors info and prices for cast iron...Wags, Gris, Volrath, Walpak, Lodge, Martin Stove and Iron, and so many more. None have this marking. I have seen a few in the Ebay area...but no one knows this marking/logo. Dont think it's from the Chicago foundries either. (as you can tell....I am sort of a collector)
Chef Jimmy...in the mid to late 50s/60's is when the Chinese and Japanese companies started making things...and some are "fakes".....that were meant to look like ones from the Foundries here. Leads and other not good metals were added to the slugs that made up their Cast Irons for the skillets and such.
I have talked with someone at the Lodge Company...and she asked me to send her a pic of the Logo and she would try and help. Haven't heard from them yet. It does look like an L with a C wrapped around it....or a C with the L under it.
Thanks for helping.....driving me nuts cuz it's a MYSTERY!