NavList:

Ken Gebhart, you wrote:
"It was made for school demonstrations."

This matches my impression, derived from old advertisements and descriptions. It's not a lifeboat sextant, not even a training sextant. It's more like a model of a sextant intended for classroom use. It does have all of the components of a sextant, and therefore at some level, it must function as a sextant. But like modern decorative reproductions, which turn up so often on ebay and are even (obscenely! revolting!) now sold at the store at Mystic Seaport, these Yoder instruments do not have a calibrated arc in any real sense. Their ability to measure angles accurately appears to be crippled. 

Starting some time around 1978 (-ish), if I remember correctly, someone got the bright idea of selling off a stock of these classroom sextants as piloting sextants, to be used for measuring angles between buoys and so on. They may have some merit in that role, but after all, this is a small market. Unfortunately, that "respectable" nautical function has created the impression among some buyers and sellers that these are sextants of a higher caliber. They do look nice!

You added:
"I evaluated it for any possible use in navigation, and decided it was not even as good as the cheapest Davis sextant."

Thank you. This may save some of us the expense of more disappointing experiments.

Frank Reed
Conanicut Island USA