Tongue depressor used to prevent mail tube from rolling around when scanned.
Fullsize image: https://diqn32j8nouaz.cloudfront.net...r_fullsize.jpg
Previously:
Mail envelope insertion machine - GIF
Pneumatic tube messaging system - GIF
Motorcycle postman collecting mail in 1912 - photo
Robot arm mailbox - photo
Mailster 3-wheeled mail-delivering vehicles - photos
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