Bristol Postage Due Handstamps and Other Cachets

Here are a few Postage Due and other cachets from Bristol (Post Office number 134), starting with an envelope with a ½^d stamp cancelled with a "BRISTOL" continuous machine cancel, with a triangular "134" handstamp (an inspector's mark ?) and a framed "1^D / TO PAY / LIABLE TO LETTER RATE" cachet.

Next here is a postcard with a black "1D/134" handstamp from December 1921.  This was because between 13th June 1921 and 29th May 1922 the Postcard rate went up to 1½^d from 1^d.

Next an example of a red "1^D / TO PAY / 134" handstamp - the postcard was posted without a stamp but was only marked as 1d to pay so appears to have been treated as Printed Matter (the rate was ½^d for up to 2 oz. from 1923 to 1940, so would be double rate or 1d postage due) despite the writing on the back.

Then an envelope with a red "2D/134" handstamp and a red framed "More to pay / above ____ oz / 134" cachet.

And finally an envelope that was underfranked with a cachet from Reading where it was posted, but then when it got to Bristol it received a framed "Not to be Found / 134" cachet and a boxed "UNDELIVERED FOR REASON STATED / RETURN TO SENDER" cachet.  One wonders if the recipient, Plymouth Philatelic Auctions, refused to accept the letter and pay the Postage Due ?