I also have a Lumicon Deep Sky filter from that era, labelled #20 on the packaging... I'm assuming the twentieth one produced! Current production versions have better anti reflection coatings but even these original versions are very good. I used it with a Bintel "Premium" (they're not really premium) 18mm long eye relief eyepiece on the Evostar 102 refractor for a 1.8mm exit pupil and visually, under 2mm exit pupil the Lumicon deep sky filters really come alive. It was the first time I saw M42 with a mild, but definitive, pink glow from its hydrogen gas. It was magnificent to look at as my previous views using another instrument was greyish. Lumicon are to filters as Tele Vue are to eyepieces, I only plan on obtaining Lumicon for filters.
Great to hear the original fleet on Lumicon deep sky filters are still out there going strong
clear skies, Mark