Many people may be familiar with Citizen’s vintage ‘Monthly’ watches, which use the 5270 movement and were produced in the late 1960s. They are also found in the guise of the ‘Moon Dater’, which was the export model. However, Citizen produced a slightly earlier Monthly model, using the 4101 ‘Jet’ movement – and this model is much less known, and is a rare beast. Made only in gold plated cases as far as I know, mine is of the white gold variety:
As can be seen this Monthly is part of the ‘Seven’ auto-dater line, using the 19 jewel version of the 4101 calibre. Unlike the 5270 monthlies, the month window is placed at the 9 o’clock position and is manually turned by the crown at 4 o’clock. The month wheel runs over the date wheel and is perforated so that the date can be seen through it.
The serial number shows production in August 1965, and ‘WGP’ refers to the case plating:
This is a large watch for its time, measuring 40mm across the case and the same lug to lug. It is also over 12mm thick, perhaps reflecting one of the reasons Citizen moved to the more compact oscillating weight movements for its automatics.
The size difference is more apparent when placed alongside a more conventional Jet model:
The 4101 movement beats at 18,000 per hour and can be manually wound, without hacking. The time is set by pulling the crown out one click, whilst the date is set by pulling in and out at the second click. The day is set by winding back and forth between 9 and 12:
It would have come in a box like this originally:
And finally a closer look at the dial and hands: