This filter is NOS from Custom Microscopy line. The filter separates a band UV to Cyan, by reflecting it at right angles to the incidence light, while transmitting nearly all of the Green through Yellow and Red. The transmission range is very wide, even in unpolarized light.
The filter makes a very good divider of an optical emission signal, into two channels or detectors.
filter specifications follow: Reflection band 360 to 490 nm with average of 95+%, Transmission in the band 510 to >830 nm with average of 95% transmission, Size 15X25 mm, Substate material is Fused Silica 1.2 mm.
Thanks for looking
For a most comprehensive assortment of filter solutions, follow the link at my store, under "Technical Data" to the Omega 'Build A Filter' tool. Millions of potential matches are available. Prices are very reasonable if you indicate "cosmetic seconds acceptable".