Let me start by saying I am not a expert when it comes to camp stoves and I've only purchased parts from three suppliers. This review is based on my limited experience. My first attempt at procuring parts for my stoves was from a ebay seller, I won't mention his name because I posted my experience with that transaction on this site earlier, I ordered a reserve cap and flame ring for my 00, some pickers and seals. The flame ring was under sized, the reserve cap had the wrong thread pitch and I didn't receive the pickers so that was a bad experience. My second try at getting parts was from the Fettlebox, I ordered complete seal and leather pump washer kits for a Optimus 00 and Optimus 96, the parts were shipped quickly and I received them in the states in a timely manner. The quality of the product exceeded my expectations. I believe the Fettlebox is the best source for replacement seals old camp stoves. My third foray into getting my hands on parts was a phone order with The Base Camp. They were very pleasant and though it took quite some time to receive the stuff I ordered they answered all my correspondence. I purchased spanners for my 00 and 96 stoves, a reserve cap for my 00, a new vaporizer for my 96 and pickers. I am very happy with everything they shipped, the reserve cap fit perfectly and the pickers and spanners appear to be original. I would recommend The Base Camp for replacement parts for your stoves. I will update this review when I test run the 96 vaporizer.
There you have it. Both are fine outfits. I've had good transactions with both; mostly Base Camp: I've bought three complete stoves from Mike over the years. A Monitor 2-pint collapsible (C-11) and an Hipolito 1 (old timers will remember when Base Camp had a regular stock of those classics); then a Manaslu 96 just a few years back. I mostly dealt with them by overseas phonecall; I liked their old-fashioned way of doing business. As for the Fettlebox, I think I bought a kit or two; alas, I'm a poor fettler or I would have done much more business with Ross! I really should get back to work on stoves....
I haven't had the pleasure of doing business with Old coleman parts yet but I plan to in the near future.