I decided to just give the answer as everyone is so close with the guesses.
Compo opened his matchbox to 21 sets of eyes over the years. I certainly thought it was more than that.Guess it's watching the programs over and over it seems like more.I've included a chart for those who are interested.I hope I didn't miss any, but if you find a program with the matchbox that's not on here, please let me know.After all the programs were taken off YouTube, it got harder to check them.(It wouldn't let me insert the chart, so I had to just list info. Sorry about the spacing but I give up trying to fix it.)
EPISODE - PERSON - LOCATION
Isometrics and After - Foggy - Hillside
Isometrics and After - Clegg - Hillside
Isometrics and After - Miss Moody - Library
Isometrics and After - Nora - Cafe
Whoops - Ivy - Cafe
The Three Astaires - The Pastor's Wife - At her front door
Getting Sam Home - Clegg - On wall during end credits
The Mysterious Feet of Nora Batty - Lady - Bar
The Mysterious Feet of Nora Batty - Clegg - Cafe
Set the People Free - Lady - Bar
Big Day at Dream Acres - Lady - Bar
The Experiment - Nora - Cafe
The Kiss and Mavis Poskit - Lady - Bar
Das (Welly) Boot - Lady - Bar
Have You Got A Light Mate? - Man with scones - Cafe
The Dewhirsts of Ogleby Hall - 4 Women - Supermarket
A Leg Up for Christmas - Lady - Bar
Beware the Vanilla Slice - Barmaid - Outside White Horse
14 Episodes - 18 different People - 8 different Locations
21 times people saw the matchbox