For sale: a standard prime lens, D FA 55/2.8, for Pentax 645D and 645Z. This lens has several unusual specifications, possibly a custom order or a prototype for performance testing. - The aperture is a fixed value, a plate with a round hole. (Approximately equivalent to f/6.7) - The autofocus switch has been removed, rendering it unusable. - Several screw holes, presumably for fixing the distance ring, are located to the right of the distance scale. - The serial number appears to be newer than the D FA 55/2.8 that was released as a product. - Compared to a standard D FA 55/2.8 with a serial number from the immediately preceding range, the coating color is different. Visually, the light transmission seems higher. Please note that this lens is not usable as a standard product. The "Size" field is set to "Pentax K mount" because there is no appropriate option, but the correct mount is "Pentax 645 mount." Pentax Mamiya Hasselblad Fujifilm GFX Leica 645 6x7