"Which CHALLENGE COINS come with my pledge?"
Or: "If I get one of the upgraded MST3K CHALLENGE COINS, do I ALSO get each of the versions listed in the previous reward levels?"
Unfortunately, your Challenge Coin reward doesn't "stack," so you only get the highest "edition" of the Challenge Coin listed in your rewards. For example, if you pledge for Experiment 400, you'd get the SET WATCHER version of the Challenge Coin, but you WOULDN'T get the BACKER or DELUXE versions included in lower reward levels.
HOWEVER: For those completionists and collectors among you, it WILL be possible to get any Challenge Coin at or beneath your pledge level as an Add-On Reward after the campaign ends. So, to use the example above: if you pledge for Experiment 400, your rewards include the SET WATCHER coin, but not the BACKER and DELUXE coins. If you want to get those too, you'll be able to do that for $40 extra for each edition you want.
Since these things are sort of a status symbol among collectors, you WON'T be able to add any version of the Challenge Coin unlocked ABOVE your pledge reward level, except (So, if you pledge for Experiment 350, you wouldn't be able to get the SET WATCHER or VIP EDITION coins as Add-On Rewards... but if it's really important to you, you WILL still be able to upgrade to Experiment 400, which will let you add the final coin for $50, since EXPERIMENT 500 sold out.)
Man, that's a lot of detail. Stupid challenge coins.