The protective device "easy-sun-guard" should not be missing on any Telrad-Finder®. If sunlight falls into the Telrad-Finder® at an unfavorable angle, the plate inside the viewfinder burns, creating the rings. The Telrad-Finder® is thus defective and can no longer be repaired.
The "easy-sun-guard" protection is simply pushed onto the glass surface of the Telrad-Finder®. This effectively prevents sunlight from penetrating.
Of course, the "easy-sun guard" can also be used as a simple Tauschutz.
Note: These parts are printed in draft quality. The surfaces are not perfectly smooth.