PPI to CDS, the range in modern postal history

After a week away I have collected the post from Dereham and thank you to contributors who have sent us material through the post.  There's a great variety in what we received this week, useful for debate and illustration.

Occasional correspondent Robert M writes from Swindon with a couple of Postage Paid Indicator (PPI) stamp items.  We have seen these before and shown them here over the years.  They were originally trialled back in 2015 and were obviously well received by direct mailers, so have been available to them ever since, with new stamp designs (usually Christmas) added from time to time.

 

 

Although the addressee will know what is inside in these cases (promotion for Age UK's Weekly Lottery in the Machin, and for Oak Tree Mobility in the White Rabbit) the perception is that the 'junk' mail is more likely to be opened with a stamp, even if it is printed on, than in an unstamped letter:

Also in today's pick up were these two properly stamped:

 

Commercial or philatelic?  The 2nd class Machin is a pre-security booklet stamp with straight edge at foot; the Roman Britain stamp was issued earlier this year.  With a CDS that certainly looks philatelic, because few POs will do this unless asked.  That one came from an eBay seller (of stamps).  The Machin is obviously valid but at least 15 years old, and that comes from the secretary of a philatelic society.

Rpbert M described the printed stamped PPIs as "almost fakes, but are they better than no stamps at all?"   I think they are better than no stamps at all, but some people who are making detailed studies of these and unstamped PPIs with all the difference licence numbers and users.  It's certainly cheaper than collecting mint stamps and they are easy to acquire - you just fill in a coupon or respond to a mailshot and these come through your door with monotonous regularity!

So which would you prefer...

... and what have I not included from the types of material that comes through the post?

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UPDATE 11 September

John G reminds me that there are other types of PPI, namely the Customer Access Indicia on mail delivered by Royal Mail but handled initially by independent companies such as UK Mail, TNT Post/whistl, Citipost etc.

John also writes:  Experiments by TNT Post showed that pictorial Customer Access Indicia increased the opening of the letter by 15% in the Netherlands and increased a response to the contents by 5% in the UK, compared to letters with non-pictorial markings. This led to the introduction of self-adhesive ‘stamp-like’ indicia on mail shots by TNT Post in the UK in 2008, and subsequently, following pressure from First Post, to ‘stamp-like’ indicia being printed directly on envelopes.

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