Here's the original unused eyeguard to fit on your vintage WWII Bubble Sextant. Marked as B&L DWG No.: 29710-24, Used on 61-90-04 Bubble Sextant. The top measures 50mm diameter (opening is 25mm), bottom measures 40mm, bottom opening is 28mm. Could be used on your 2" telescope eyepieces or possibly even binoculars. Unused.