Interesting Visor Shape-retention Idea

[stonemint]

As we know, over time a schirm can bend the pasteboard so that the band is bowed out at the bottom. A lot of people use thread, but this leaves a mark in the piping and wool. I thought this seller on ebay had a good idea--he uses what looks to be Mylar (but I forgot to get his name to see if he buys these, or if they are home-made):

[stonemint]

Anyone seen or done this before?

[MattS]

I know Kingform Cap Company of New York uses these on their US Navy officer caps when they are shipped from the factory. I don't know if any other maker uses them.

[stonemint]

Here is another question. I have seen these "hat-stretchers" sold over the years as being german/TR period. Anyone have any ideas who made them, and when they were made? Does anyone have one, and are they any good?