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Original Video Credit: IG/kim.jacobi
Unlike modern peepholes that only look straight ahead, these older adjustable viewers used a movable internal lens assembly that could swivel inside the brass housing. By shifting the center mechanism, the homeowner could scan different areas outside the door without opening it.
From the outside, the lens appears to glide around like a mechanical eye as the internal optics pivot behind the glass. The movement changes the viewing angle while keeping the peephole itself mounted in the same position on the door.
These specialty viewers became popular in some mid century homes and apartment buildings because they offered a wider field of vision before compact security cameras existed. Many were built from solid brass and designed to blend decorative hardware with practical home security.
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