For a while in the late 1980s/early 1990s I used to pencil my pages onto thin paper, then trace the finished version in ink onto Bristol Board via the glow of a Lightbox. Eventually I went back to just penciling and inking on the same board as I found using the Lightbox a bit of a strain on the eyes.
I threw away most of my penciled pages once the inked versions saw print, but I did keep some. Case in point the penciled page for a chapter of Combat Colin's Prehistoric Adventure that appeared in The Transformers No.280 (28th July 1990).
I don't sell my inked Combat Colin pages but I am selling this penciled version on eBay at present. (Auction ends tomorrow, Sept.22nd). I know some collectors like to see the pencil art so they can see the construction of the strip. If you're interested, visit my eBay page by clicking here.
And if you're curious to how the finished version turned out, here it is: