GB Stamps - Matching Scott & Sg Numbers

Have had no luck finding a solid and consistent resource that equates SG numbers to Scott numbers for Great Britain stamps, and while most are not hard to find, there are a few that are more difficult to nail down. I have used several sites to match up some of the less obvious numbers, but wonder if there is another resource that might be available, notably for Machins.

I've specifically had no luck in finding the corresponding numbers for:

Scott MH294 = SG ?
Scott MH460 = SG ?
Scott MH461 = SG ?
SG U2957 = Scott ?
SG U3095 = Scott ?
SG U3920 = Scott ?

Any help is greatly appreciated. Thanks!
Martin

You might help us along by describing the stamps.

There is no cross reference because the catalog publishers aggressively come after anyone who tries to publish such a list. They falsely claim that catalog numbers are copyrighted when here in the US this has been rejected by the courts. But it does not matter, receiving threatening demand and desist letters from their lawyers is typically enough to scare everyone away. In my opinion this strong-arm practice has damaged the hobby since it has served to prohibit digital and online growth.
Don

BB Stamps, a UK dealer at https://www.stampsforsale.co.uk, does list both SG and Scott catalog numbers side by side in its online retail catalog. That's the closest thing I've found to a cross reference.

Chris

Scott is well-known to be terrible with cataloging Machins. All kinds of omissions, errors, etc. They're the last reference you should use for Machins.

I can check tomorrow but there are some Scott Machins not in SG. SG does not separate the non.EME and EME for some issues if there was no other difference like tagging.

I tried to search online, starting with the first stamp. Seeing that for 2nd class blue Machin there are 49 versions, I understood that I'll never have a good or even average Machin collection.

Thanks for all the replies... they certainly correspond to and explain what I have found (or not found).
Machins, though interesting to collect imo, are certainly a rabbit-hole that is further complicated by the conflicting catalog numberings. But I appreciate the insight and will just figure it out as best as I can. It's certainly a small issue in the grand scheme of things! :-)

Thanks!
Martin

Do you know these sites:
http://machinmania.blogspot.com/
https://adminware.ca/machin/
http://goscf.com/t/10785&whichpage=1

I can only help on one since my Scott Machin ends at 2014.

Scott MH294 is a self-adhesive 2nd Light Blue. This issue had 3 printers but SG Concise does not differentiate like Scott.

There are two ways to determine printers - perf shape and perf measurement using Deegam. By perf measurement, I believe it is Walsall. The images are too small in Scott to positively determine perfs.

From about 2012, these nvi's had a security overprint that showed the source and year. From that point onwards, identification should be easier.

SG numbers from Concise are very incomplete. From the specialised they are somewhat more extensive, but SG's strength is not in Machins.

I went back and double checked my SA 2nd NVIs and found an error

Using Deegam as the source and checking details (descriptions, first issue dates) in Scott, I can associate all 3 Scott varieties to a specific printer.

SG assigns one number 2039. In my numbering system, they are 2039-W,2039-Q, and 2039-E.

Scott MH292 - Walsall. Thin value, The design is 0.7mm from right frame and the determining factor.

Scott MH293 - Questa. Thickest values, design about 1.0mm from right frame, more U shaped die cuts. phosphor bands 4 or 5mm (not 4.5mm like Walsall and Enschede). Perf is 15x14¼ (not mentioned in Deegam). Others are 14¾x14.

Scott MH294 - Enschede. Thicker than Walsall values, design 1.0mm from right frame. Perfs more sinusoidal than Questa.