Uh… I don’t think I’ve been mysterious at all, one bobbled attempt at humor aside.
I have a signed, limited-run stretched-canvas serigraph that’s 2x4 feet, or 2’x4’, or 24"x48", or 23-7/8 inches by 47-3/8 inches, depending on who’s asking (or cares). It’s presently in a rather plain unglassed frame and was originally hung in an acrylic box for protection. I want to reframe it more conventionally for a room that gets a little too much sunlight to be casual about the glazing, since its appraised and catalog value is… considerable.
I have other pieces framed with both Museum Glass and Conservation Clear. MG is amazing stuff - it’s not only invisible, but since it reduces reflections off of the work itself it gives a “more transparent than unglazed” sort of effect, the way exceptionally well displayed museum works (with very carefully controlled position and lighting) do.
However, I find $1200 to frame it very simply, with Museum Glass, to be up into anal-rape territory. As in usual in "professional framing, this is approximately a 5X markup on materials and there is very little esthetic judgment or skilled effort to apply, since I’m specifying the materials and it’s a plain, single-element rectangular frame. I can and have framed works like this for public and small museum display, leaving only things like acrylic box construction to pros… and paying an appropriate price for such work, not the vast markup a “framing professional” would apply to the same box built by the same shop.
Other than that I’m not identifying the piece in question, for personal and insurance reasons… is my inquiry about a reasonable retail source for Tru-Vue Museum Glass in this size still mysterious? 
On to piece two. (You did read carefully enough to note that I am talking about two completely different pieces of art, right?) This one is a museum-grade but not terribly valuable print of a famous graphic art work. I could buy or replace it for well under $100 (maybe under $50), but I’ve had this print for a long time, and the circumstances of its acquisition and various subsequent history make it of great sentimental value.
It is, however, about nine inches (9") wide and thirteen feet (13’) long. It is usually framed in three to five separate frames, and I’ve come close to doing it that way, but I finally have a wall that can take it in all its glory, and I want to do a one-piece frame, fully recognizing all the construction, mounting and (someday) transport problems. Nothing here poses any problems except the glass.
The traditional solution is to use multiple pieces of glass (or acrylic) with the butted ends polished so that the seam is almost invisible except in strong cross-lighting. I’m willing to put up with that. I’d like to do it in MG, but for cost reasons I might come down to one of the Tru-Vue grades that is less amazingly amazing - as long as it’s reasonably nonreflective and pretty good in UV protection. Tru-Vue’s acrylic Optium would be ideal, as it’s almost as good as MG, but I can’t find reliable prices on it. The rest of the frame will be a laminated backboard and a simple shadow-box rim.
Suitably un-mysterious?
The latter work is, of course -
Escher’s *Metamorphosis II *- a print issued directly by the Escher Museum a few decades back. One day I’ll have a wall long enough for a solid framing of Metamorphosis III… same print, extended to twenty-two feet. (22’)