Leica's M-mount 135mm with viewing aid — 'spectacles' attachment brightens the tiny 135mm frameline.
The Leica Elmarit-M 135mm f/2.8 with Spectacles is a version of the 135mm telephoto that includes built-in viewing spectacles — small optical elements that magnify and brighten the 135mm frameline in the M rangefinder viewfinder.
Same optics as the standard Elmarit-M 135mm f/2.8 — the spectacles are external viewing aids attached to the bayonet mount that improve the visibility of the tiny 135mm frameline. At 135mm the rangefinder frameline is very small.
Leica M mount with viewing spectacles. The spectacles fold out of the way when other framelines are needed. Manual focus with rangefinder coupling at 135mm. The viewing aid helps but 135mm remains challenging on rangefinder.
Available used at mid-range to professional prices. The spectacles variant is less common and of collector interest. The 135mm on rangefinder is inherently challenging — the spectacles help but don't solve the fundamental limitation. For Leica M collectors.