11p Regionals with Single Phosphor Band

I was recently working on my Machin regionals collection and came across a stamp that I purchased some years ago but never put into the collection. It is an 11p Northern Ireland regional with a single left band.

The 11p regionals were issued in 1976 to pay the basic airmail letter rate to zone B. During their lifetime until withdrawal in 1980 they also paid a few other rates. They were photogravure printed by Harrison and Sons.

As with nearly all Machins, except those that paid the basic second-class rate, they were issued with two phosphor bands.

The catalogs note that both the Northern Ireland and Scotland 11p regionals are found with a single band, either a left band or a right band. The only explanation I found was in the Deegam Handbook, where Douglas Myall says that the omission of one of the two bands "was caused by underinking of the phosphor cylinder."

In the image of my stamp above, you may be able to see an indication of the left band and that there's no similar band on the right. With a UV lamp, I found that there is actually a bit of phosphor at the lower right; hopefully that doesn't decrease the value of the stamp too much.

And speaking of value, therein lies a tale. The MCC Catalogue (2008 edition) values the Northern Ireland right band at £15 and left band at £75; the Scotland right band at £100 and left band at £65.

Douglas Myall only gives price ranges in the Handbook, and they are reasonably consistent with the MCC values.

The recent Stanley Gibbons Specialised Volume 4 Part 2 lists the Northern Ireland stamps at £6 and £9 respectively, and the Scotland stamps at £40 and £35.

Could this be a case where Gibbons' prices are actually lower than true market value?

--Larry