Hello, I have been studying more stamps today and these were just two of them.  Can you spot the difference? 

ok I will tell you. Both are SG 440 from the GB George V 1934 - 36 definitive issue and both are normal watermark Block Cypher (W111) 

But, the left stamp has a larger white margin than the right stamp.  Specialised GB catalogue as N 49, termed small format, for the left stamp and N50, termed intermediate format, for the right stamp.

No catalogue price difference as far as I know, but if you have inverted or sideways watermarks you will find there are price differences, and in some cases quite significant.

Always worth checking what look like simple low value stamps for variations.

You can see these and more, including sideways and inverted watermarks in my Bidstart Store  at http://cddstamps.com/bidstart-sales/  if you are looking to fill some gaps in your collection

Have a great philatelic weekend.. Michael

www.cddstamps.com