Here are two 4.37 inch diameter prisms from a Hilux wide screen
One is flint glass (unk n/nu) with min thickness .09" and max
thickness 0.76 inches for angle of 8.7 degrees.
The other is crown glass (unk n/nu) thick .14"/1.62" angle 18.7 deg.
The optical quality of these is good. I put the cemented prism
in front of a 4 inch scope and the worst effect on image seemed
to be residual color.
These prisms were cemented into an achromatic pair and mounted
in a an assembly that allowed tilting so that two of achromatic
prisms could stretch the movie image anamorphically.
They were starting to delaminate so I soaked them in toluene for
a time and they finally came apart into the prism's in the picture.
What is for sale is the crown prism, the flint prism and the
anodized wedge shaped cell to help improvise a mount. They are
essentially perfect with only very minor edge chips,
the air surfaces of each appear to be coated.
I think if you used the two prisms together in some clever way
you could make a zero-deviation objective prism. That is a prism
that gave spectra but did not deviate the line of sight which
would make guiding easier. I notice that they the prisms can
rotate relative to each other in the cell. Slight rotation would
spoil the achromatism and produce a "dialable" amount of
$50 for a set. I have two sets available.