This is the G063346331 model from Qioptiq Photonics, a 22.4 mm diameter UVFS mounted double-concave lens with an effective focal length (EFL) of -40mm. The lens is made of UVFS material with the Mal-1965 identification.
The lens features a symmetric concave-concave geometry, with a center thickness of 1.5mm. The first radius of curvature (R1) is -40.388mm, while the second radius (R2) is 40.388mm. The lens does not have an inner or outer radius.
The lens is designed for use with a wavelength of 355nm and comes with a front and back coating of Qio AL RALVIS AOI 45. The lens shape is spherical.
According to the vendor's information, this item is in stock and can be purchased directly from the Qioptiq Photonics website. The link to the product page is provided for your convenience.