"Antique float glass"

That's what the planning officer said we had in the refurb house (Grade B listed), when he told us it had to be preserved at all costs, and we couldn't fit double glazing. Two things to say about that.

First, float glass was only introduced in the 1950s. Second, it was actually 2mm greenhouse glass, as we were told by the man who fitted it in the first place. The planning officer actually meant to say hand drawn glass, horribly wrong though he was. Further conversations to be had.

But this, this is hand drawn glass. Look how easily your can't see through it.