Bushnell Xtra-Wide
The "Xtra-Wide" series of binoculars feature larger than normal fields of view. Some models employ mirror instead of prism elements. Besides the models shown below, others in the series include a 4x21 (900ft@1000yds). The 7x32 and the 10x50 seem to have been discontinued, but a similar 7x32 may be available from other brands such as Orion.
Xtra-Wide 7x32
Mfr: Kamakura Optical? (marked "Japan", no J- marks)
Date: late 1990's
AFOV: ~93 degrees
TFOV: ~13.3 degrees, 700 feet at 1000 yards
Eye Relief: ~8mm
Prisms: combination of mirrors and prisms
Serial Number: AH01105
This unusual super wide angle binocular uses mirrors for the first two reflections in combination with a prism for the rest. US Patent 6188516 by Naomi Watanabe (Kamakura Optical) appears to describe this design. Mirrors were likely used due to the cost and bulk of a prism required to cover such a large field of view. The exit pupils are nearly round when viewed straight on but vignetting is visible at angles in two directions (from the prism). The optical image is very good on axis but there is a large amount of astigmatism off axis as one might expect. Distortion is fairly well corrected for such a wide angle. According to the patent, an aspheric element is used (18 in diagram above from the patent). A bit of extraneous reflection is visible towards the top of the field. When compared to a normal porro prism binocular, the mirrors do result in some brightness reduction, though it is not very noticeable in bright daytime viewing. The mechanical design of the binocular is very ergonomic, with a rubber coated body, rubber eyecups, and an easily reachable focus knob. This is an interesting binocular to view through, due to its unmatched field of view, but the short eye relief limits the comfort level.
Xtra-Wide 10x50
Mfr: Kamakura Optical? (marked "China")
Date: late 1990's
AFOV: ~95 degrees
TFOV: ~9.5 degrees, 500 feet at 1000 yards
Eye Relief: ~8mm
Prisms: combination of mirrors and prisms
Serial Number: AI02548
The 10x50 Xtra-Wide appears to have the same body and eyepieces as the 7x32 with larger 50mm objective tubes. Performance is very similar, except that the 10x50 image has a slightly yellow tint whereas the 7x32 has a slightly blue tint. This could be a result of different glass types used. Also, production for this 10x50 seems to have shifted from Japan to China, as evidenced by the marking on the end of the hinge.