That’s who refilled the tank and supplied it last. Linde hasn’t been around for a long time.

It means Linde. Here is a cylinder from Linde/Union Carbide that was made in 74.

Before end of WW2 linde used swastika as company logo on tanks. After WW2 they used the window. Many old tanks had the swastika changed to a window, often very poorly. This is a tank from 55 that never had a swastika stamp, just a window stamp. Lots of poor information about this on the Internet that is mostly just forum posts. People see the window and instantly incorrectly think it’s an altered swastika. Look at pictures of other window tanks and you can see they are all done poorly prior to 45 and are clearly altered. Starting in 45 they all look perfect and sharp because they are original window stamps.

This is not one.

No it isn’t.