As the 19th century approached Arabic Numerals were used and as the 19th century progressed the Arabic minutes were lost from the dials altogether.
The earlier style of flowers, fruit and foliage to the corners and arch were being replaced with scenes depicting famous people, religious stories and legends.
Be careful here: the forms of cases and dials changed very gradually according to local fashion and subtle differences can be very significant.
Like knowing when certain features were introduced or certain materials became available.
A few simple things that can point you in the right direction and at the correct period for your antique wall clock, advertising clock or bracket clock.
The first fully-enclosed clock known dates to 1665, the one pictured here was made by Edward East in London, dated 1685.
Now instantly recognisable as a longcase, or "grandfather" clock.
Also, the British Horological Institute, at has many other links that will be useful.