I think it may be a special use EP (spotting scopes?):

"JIS Class 4 weather proof construction makes these eyepieces more durable"

Sure is a weird looking dude!

$339 for an EP with 3.6 mm eye relief? No thanks!

Phil

Jon Isaacs wrote:

http://opticsplanet.net/pentax-eyepiece-xo-20.html


It looks to me like it is a Pentax XO-5 (Duh)

I especially like the eyerelief:

XO 5

Lens Structu 5 elements
3 groups

Focal Length: 5.10mm

Apparent Field of View: 44°

Eye Relief: 3.6mm

jon