It's been some time since I have had a calendar this size and even better being in sought-after Mahogany; standing 11" tall, one of seven I have just purchased from a private collection.
The four knobs to each side are used to move forward and rewind the day, date and month behind the three glazed apertures. All in full working order. The underside has been more recently covered in a green baize to protect any wooden desk top.
Excellent condition, the footprint measuring 7 1/2" x 4" and standing 11" tall.