Michael Hoey writes - Your old photo W542 shows St Mary's Church without the clock. It also shows 2 young yews, at 4/5 feet high, which are now
20-30 foot monsters, blocking a clear view of the church. The original clock was mounted on the East wall of the tower [right face in the photo].
The clock bears the date 1793, removed when the upper part of the tower was rebuilt in 1908. For nearly a century, out of use, it lay, in parts, in the
tower until 1998, when, lovingly rebuilt by Chris Dennis, was re-installed in time for the new millennium, this time on the South face.
It has kept good time, with a little help, although it is running a couple of minutes fast this week.
I have a photo similar to yours dated 1927, but in mine the yews are smaller, making your photo after 1940-ish
 
Debby Cadwallader writes - Re your enquiry about the photograph of St Mary's Church, Princes Risborough
The clock was removed from the tower in 1908, when the upper part of the tower was reconstructed and the present spire of Bath stone built,
as in the photo. The clock was restored and installed on the south side of the tower for 2000. From 1908 until 2000 the clock was stored in the tower.