Chamonix 4x5 film holder. How to tell if Film exposed?

[Eric James]

The most recent Chamonix plastic 4x5 holders have an EKG (heartbeat) symbol on only one side of the dark slides. The dark slide locks are tiny (2-3mm) red buttons.

[Sal Santamaura]

The most recent Chamonix plastic 4x5 holders have an EKG (heartbeat) symbol on only one side of the dark slides. The dark slide locks are tiny (2-3mm) red buttons.

Interesting. I hadn't gone to the Chamonix page recently and didn't know its 4x5 holder are now plastic. When Riteway 4x5 holders had similar dark slide interlocks, they weren't compatible with Linhof cameras. I wonder whether Chamonix's product is.