Here's a close-up of the scarce incuse marking. The LTD marking fades away (disappears) after the captial letter "L". This is the first one of these I've come across with this marking on a U-1542. Cool find at an insulator show! :-)

Another interesting feature is that it was glazed upside down as the top of the crown is unglazed.

For a look at the reverse crown incuse marking [id=151292721]