Merriott Undated Circular handstamp (UDC) used in 1844

According to the British County Catalogue published in 1990, Merriott's UDC was issued on 11 December 1840 and is only known in GPO archives.

Below is an example of the UDC from March 1844.  The example is quite degraded, which would imply to me that the handstamp had had some use prior to the example below.