Question About Finding Watermarks On Stamps On Envelopes

So i've finally had a look at some of my old acquisitions today and according to the stampworld website, some of these are worth quite the pretty penny, if only I knew where to look for the watermarks on them. I hope I shouldn't have to remove them that's for sure! Could anyone advise on where the watermarks are on these stamps? Also, I reckon that nobody actually pays the values indicated in the catalogue on this website, is that right?

The first is a George V 1/2 penny stamp, and the other two are the 1954 surcharged issues of the GDR, 16 and 48 pfennig. All have been used.





Thanks in advance!

Ok, I guess I could have found that out myself. Thing is, if I could obviate the need for stamp watermark solution or an expensive optical apparatus and also not have to remove the stamps that'd be much better. Is there even such a way to go about this? I'd really like to leave the stamps as they are, attached to an envelope.