Here are ten covers from Bath, starting with one from Bath to Antwerp in 1737. It appears to have been prepaid 4d and has been stamped with a circular "PD" handstamp that indicates it was paid to its destination.
Next is a free cover to London dated May 1802, with a straight line "BATH" and a nice red London "FREE" mark.
Next a c ouple of "TOO LATE" covers from 1821 and 1824. The "TOO LATE" indicates the covers were posted too late for the day's post.
Moving on, here is a One Penny Newspaper wrapper with a Bath "53" 3-bar vertical oval cancel.
Going away from cancellations for a moment, the envelope below dated 1885 is from the 'CYCLISTS' TOURING CLUB" (renamed from the Bicycle Touring Club in 1883 because a number of the members rode tricycles.
Perfins were used to prevent employees stealing stamps and getting money back from the post office. The large "S" below was used in 1902 by Stone, King, Stone & Thomas, solicitors in Bath.
The Telegram below was used in 1918 to indicate that the sender was going to arrive by GWR in the envening. It has a "BATH / T" single ring cancel which was normally used on telegrams.
Here is another perfin from 1952, a "BCC" used by the Bath City Council - in this case by the School Medical Department.
And finally from 1960 an envelope addressed to a patient at St Martin's Hospital Bath but marked as "Not Known", opened and sealed by the Post Office to get a return address.