To the best of my knowledge the Telstar we are talking about here is not the same as the Telstar music distributor which started in the 60's as suggested in the magazine scan below, although please let me know if you have better information. Telstar is a UK company which began life in 1993. They started out by selling discounted video games in 'double packs'. As far as I am aware it was only games for the Mega Drive, Master System and Game Gear then later they also released packs for the PC. Telstar went on to get the UK publishing right to 7th Guest.. it all went down hill from there until they were bought out by 'Take 2' in 1999.
The packs were advertised in the Sega magazines of the day (Sega Pro) and also sold through popular high street shops such as WH Smiths and HMV. Below is an advertisement feature from issue 31 of Sega Pro (Easter 94).
As you can see from the above advert most of the Double Packs released were for the Mega Drive, in fact there are 20 mega Drive Telstar Double Packs in all, as can be seen listed on Guardiana (A French Mega Drive site). I do not collect for the Mega Drive but I have been told that these are very difficult to find and perhaps only pop up on ebay once maybe twice per year. Below is my Mega Drive collector friends set of 6 Double Packs.
The main reason for the rarity of these packs, other than the fact that comparatively few would have been sold, is the packaging. The outer casing is just thin clear plastic with a paper insert to cover the two original game boxes.
The games sit back to back so that the hangers fit through a gap in the outer casing. The only actual difference with the game boxes inside is the Telstar stickers over the original barcodes and smaller T F&G (Telstar Fun & Games) stickers on the front covers.
As you can see from the picture below Telstar and Sega Pro had a bit of a relationship going..
The Master System double pack I've shown here is the only one I have ever seen, I found it in June of 2007 on ebay. I ended up paying just over £30 for it which I was surprised at as the auction was quite poorly done. I would say that you shouldn't really have to pay more than this but it's one of those difficult to value items. The Mega Drive ones are more common (if you can call them that) as there was such a large range avaialble but apparently just 3 each for the Master System and Game Gear.
As with any of my articles if anyone has any more information or even just pictures they can provide then please let me know in the comments link below.