In a manual supplied with a Jason refractor, there is evidence that, by 1967, Jason was hedging its bets against breakage of eyepiece solar filters. Hesitancy against using them is found in that year's edition of "Jason*Empire Telescope Techniques with Illustrated Studies," published by Jake Levin & Son, Inc., a manual included with Jason telescopes. On Page 20, "Advanced Celestial Study -- Daytime Viewing #14" reads, with the boldface and capitals as they appear in the original:
"Though many telescopes come equipped with a red sun filter, NEVER rely entirely on this for eye protection. Never view the sun without doing these two things: (1) Have the sun filter in position, and (2) wear dark glasses or use dark developed film... It is better to reduce the amount of light from the sun by using the smaller diameter opening on the objective lens. Most telescopes have a smaller inner cap as part of the moisture cap."
Those are all the right steps to take to reduce the risk, yet even Jason knew at the time that it was better not to use these filters at all. The prior study dismisses them as unneeded. "Advanced Celestial Study -- Daytime Celestial Viewing #13" first describes how to use or even make your own solar projection screen, and then states:
"This is an added safety protection and you can see as much from viewing the sun in this method as viewing it directly."
It appears that there was inertia in the marketplace, as though people expected to receive eyepiece solar filters with their new telescopes for some time after at least this manufacturer was nervous about delivering them.
Special thanks to member jungus57, who sent me this book, hoping it would find an appreciative home. How suitable that it should help unravel the history of unsafe eyepiece solar filters.