Graham Beck has created many interesting videos for philatelists on YouTube. His channel is called “Exploring Stamps’ and it has a huge variety of subjects to learn from.
This video is 30 minutes long and shows a top stamp dealer evaluating a collection of early UK stamps (penny blacks, blues, reds). On the one hand it is quite specialized and advanced, but it also makes some really important points about condition and value that are universal stamp collector matters, so it has interest for general collectors too.
