Ian Rose has replied to this post below with his comments. (Click on comments at the end of the post to view) Many thanks Ian for adding to this debate. Douglas Mayall has also responded.
James Skinner as you say does not list them, and I appreciate non marginal singles could pose problems for dealers. However, when the stamps were first printed due to the phosphor layout so close to the perforations and the different papers it was advised to collect these as marginal pairs or singles in order to aid identification. This is how dealers should supply them.
As all date blocks and cylinder blocks consist of margins attached they (intermediate paper)should for completeness (in my view) be listed and priced in both Gibbons Vol 4 and Connoisseur.
The MCC catalogue has a lot of faults, but it is a good reference book, it does list and price these and short / inset bands too. Some time back Larry explained the way to identify these stamps, this is
worth another read I think.
Douglas Myall (Thanks Douglas) informs us
"The best way of distinguishing Byfleet TR3 papers is to have identified samples of all of them (marginal date strips are ideal) and stick them onto a piece of black card, one below the other. Lay an unknown sample across these strips at right-angles so that they can all be seen together under the lamp. Because daylight contains some UV
these benchmark strips should not be exposed to it or they will become
unreliable"
The Adobe version, to be published in April, has a new appendix with publishing dates. These are linked to the catalogue lists at level 3.
My Original Post
I was also shocked to learn that (according to the Gibbons specialised vol 4) they do not recognise intermediate paper (TR3). After all the work put in by specialists to study and record details, they have now decided just to do away with them and class all TR3 intermediate papers as bright.
As I say I was shocked. This is the first I have heard of this. Has anyone else heard of another Machin specialist catalogue that has scrapped intermediate papers from its lists?
HOW I FOUND OUT.

I was intrigued to learn that the 9p Machin (Orange & yellow) was staying with us (for the time being). So I got my collection out of cold storage to cross check that my my date blocks were current against the 9p values listed in vol 4. I was so confused, half of the dates I have were not covered by Gibbons. I read up on the notes to find out why!
This means that the intermediate cylinder block cat by MCC @ £15.00 is now only worth £3.00. My inset left cylinder block (intermediate) does not exist!! How crazy is that?
At least I can possibly add to my collection of 9p (dull) date blocks and cylinder blocks, even if the intermediate blocks I have been collecting for 6 years are now bright :-)
Now you are as confused as me.
To recap on papers before someone at Gibbons decided to alter things.TR3: This is the main term for paper that was used by Royal Mail for the Byfleet printings, there are (were) 3 types to be found to date with variations of the amount of OBA (Optical Brightening Agent) in the coating.
They (as far as I know) were listed and known to specialist collectors as Dull, Intermediate and Bright papers. Listings are given secondary codes by collectors as - d, - i, and - b.
TR3-d = DULL
TR3-i = INTERMEDIATE (no longer exists) but you can call it bright.
TR3-b = BRIGHT
RMS Paper is known as (Royal Mail Standard ) or (Specification) This is the paper currently used at Dunstable for all current printings , Known in certain circles as ATN (c) This has a cream PVA gum and is dull in appearance, developed and designed by order of The Royal Mail to get near to that of HS2 used previously by Harrison's at the High Wycome plant.