Hi,  given it has been raining all day that gave me time to do a lot more with the stamps that are cluttering up my study. I found these. They look different and there may be a good reason but one reason is I noticed is that the perforations are different. well they look different to me.
See detail below.

The perforations on the right stamp seems to have more rounded holes and are cleaner cut. After some research I found that there were in fact two printings from different perforation machines of this 1997 issue of high value definitives. One printing used a Kampf perforator and the other used an APS Perforator - if I have not expressed this correctly I am sure I will be corrected. There is in fact a thread on this on Stampboards for those of you who know that great Stamp group.

Simply put a Kampf perforator produces holes that are clean  while APS holes and not so clean
And for the real geek philatelists out there the APS  stands for Ab Produktion Svenska, the initials of a Swedish firm which manufacturers perforators.

I just so enjoy learning all this new stuff, don't you :-)

Best wishes.. Michael
www.cddstamps.com