In general astronomical filters are a combination of two or three Schott colour absorption glasses which are selected to provide a particular spectral response, e.g. a matched to the historic Johnson UBV photometric system. The glasses are laminated into a single-piece optical assembly.
UBVRI passbands, M.S. Bessell, 1990, PASP, 110, 1181
"UBVRI Filters for CCD Photometry", M.S. Bessell, 1995, CCD Astronomy V2, 4, 20
"The Hipparcos and Tycho Photometric System Passbands", M.S. Bessell, 2000, PASP, 773, 961.
Section 8.1.2 "Photometric Systems" in "The Handbook of Astronomical Image Processing" by Richard Berry and James Burnell.
Section 5.3.1 "Photometric Systems" in "CCD Astronomy" by Christian Buil
Standard Photometric Systems, Michael S. Bessell, 2005, ARA&A, 43, 293.
Michael Richmond's Photometric systems and colors
A "Harris" V-band filter is a glass sandwich designed by Hugh Harris (USNO) in order to yield small colour-terms and was developed at KPNO. The listed glass combination for the "Harris" V is "2mm GG495" + "2mm BG39". Other used combinations for the V-band include "2mm GG495" + 3mm BG40" and "2mm GG495" + 3mm S8612".
SBIG's Research Grade UBVRI Filters follow the "Bessell filter prescription of the Johnson-Cousins filter set specifically designed for photometry with CCD cameras". These filters have an anti-reflection (A/R) coating and are 5mm thick. ( V-band filter transmission curve).
OPTEC's V-band is labelled as a Johnson/Cousins V Filter (Bessell) ( Stock No. 17447, 50mm diameter, multilayer A/R, 5mm thick). Compared to the SBIG V-band filter, the OPTEC filter has an more extended red response by 20nm.
Cousins/Bessell vs. Johnson Filter Standards by Gerald Persha (President, Optec, Inc.)
Quantum Efficiency of SBIG CCD Cameras