NavList:

And yet there's a bit of a contradiction here, it seems to me, in the
attitude of many small-boat navigators; those who prize their expensive
sextants, reading to 0.1 arc-minutes, and wouldn't be seen dead using a
plastic sextant, no matter how good it may happen to be. I raise this matter
at the risk of reopening old wounds here, but it would seem to me that if
HO249 is acceptably accurate, then so too would be a decent plastic sextant.
I'm not arguing against Gary here; I simply don't know whether he is a
member of the diehard posh-sextant brigade or not. But they exist, and for
them, would the 1-minute precision of HO249 be considered good enough?