It appears that Mi 45B in many offers may actually be Mi 45A. The problem is that in my opinion the Liechtenstein 2 Rapen, yellow stamp, is not the very rare Michel 45B with 12½ perforations but a much less expensive 45A with 9½ perforations. This is a very subtle difference but 45B has a Michel catalog value of €500.00 and 45A a catalog value of €6.50!
Both look very much identical, however I counted the perforations on the 2 Rapen stamp displayed which indicated to me that it was definitely a 45A and not a 45B. I also noted this hard to detect substitution elsewhere for this stamp listed for sale on other ebay country sites. Normally, the 1921 A series is more expensive than the 1921 B series with this one notable exception.
If you doubt my analysis, you might like to have a professional philatelist confirm my opinion.
Sincerely,
Cort MacLean Johns

I'm no expert on these stamps but the difference between perf 91/2 and 121/2 should be quite noticeable! I do not know how many perfs difference it makes, I think it is perf121/2 or 91/2 in 2 centimetres so it depends on the height of the stamp but I reiterate its quite a difference and noticeable, I'm surprised at the confusion and that someone mis-describes the stamp, is it worth reporting?

Thank your post!
When one takes a look at the Michel Liechtenstein catalog, it is clear that 45B is not listed with the more common 1921 B Series. The set price does not include Mi 45B. The 2-rapen, yellow, 45B stamp is listed separately below the rest of the B set. The 12½ perforation set starts with a 2½ Rapen (46B) and runs through to the 15 Rapen (52B). "Satzpreis B (7 W) ** 460,--"
I do understand that it is not easy to untangle some of the Michel Catalog details. This is especially so in this unusual case where a B 12½ perforation stamp is more expensive than the usually more expensive A 9½ perforation series. However, when one reads down a bit further one will see, "Zähnungs-Abartem; Amtlich nicht ausgegeben 45B,**500,00". This stamp is rather rare and hard to find on sale online. I cannot judge whether those who are posting the 45A stamp as a 45B are doing it on purpose. However, Delcampe, eBay and other online services should immediately challenge instances where there seems to be an obvious 'switch' as you rightly have observed. On the other hand there may be those who see this as an opportunity to mislead the stamp buying public, certainly when including it with other 1921 B series stamps and demanding unusually high prices for this rogue.
I have yet to find here, eBay, or elsewhere what would appear to be a genuine 12½ perf. 45B for sale.
Best regards,
Cort MacLean Johns

Is it worth reporting? Well that depends on whether one find a Michel catalog variance of €493.50 between a Michel catalog value of €500.00 and 45A a catalog value of €6.50 significant! That's a misrepresentation of over 7500% it would seem. Maybe I'm too old-fashioned an auditor to write that off as "immaterial"?

I don't have the relevant catalogue so can't say whether the sellers are purposely misleading you!

Yes, not all catalogs agree on commonly assigned numbers. However, when a seller states "Mi.XX", they are referring to the German language Michel catalog. In cases where, they offer for sale a Mi 45B with its photo and it does not appear to have 12½ perforation but a Mi. 45A with a 9½ perforation (which is usually noticeable without a magnifying glass), they should take their offer down. Once they have read their Michel Catalog more precisely. However, if they do perchance have a Mi45B with a 12½ perf., then I expect that there would be many collectors who would be interested.
Personally, I cannot recall having seen a Mi. 45B that looked like it had a real 12½ perf. However, I should add that it is frustrating to have a blank space for a Mi. 45B in one's FL album, yet never find an authentic one to fill that blank space.