3" diameter FUSED-SILICA (quartz), 1/10 wave, Edmund Optics precision reference optical flat, 3/4" thick, in foam-fitted storage case, with interferogram, amazingly flat and smooth reference piece, replacement value $421. As it is designed not aluminized, can be used as a test plate to evaluate diagonals, etc., using the emisssion lines in ordinary fluorescent lights. Like new, received in an astro trade, I don't believe it has ever been used. Serialized 1/10 wave certification label on the edge of the glass. 59502801 and several other numbers appear on the case label.
$185 shipped in CONUS, paypal encouraged.