I never had an intention to collect these (I used to get most of the MP toys from HLJ in Japan, so didn't get too many during their time of release), but a couple of bulk purchases from BBTS, and I'm now up to 42.
I don't want to collect them all... which would be very difficult, especially with Exhaust not seeing a legitimate release... but these are a novelty for the collection. It's just a shame that the coins don't come out without pulling apart the envelopes.

Approximate release order of mine (I did up this list before finding the list in this topic)...
2011 - DOTM Supreme Class Optimus Prime (Jetwing)
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2012 - MP-11S - Sunstorm
2012 - MP-12 - Sideswipe (Lambor - first release)
2012 - MP-14 - Red Alert (Alert - first release)
2012 - MP-13 - Soundwave
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2013 - MP-15 - Rumble/Ravage
2013 - MP-16 - Frenzy/Buzzsaw
2013 - Encore Fortress Maximus
2013 - MP-17 - Prowl
2013 - MP-18 - Bluestreak (Streak - first release - light grey deco)
2013 - MP-19 - Smokescreen
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2014 - MP-12G - Gen2 Sideswipe (Lambor - black deco)
2014 - MP-13B - Soundblaster
2014 - MP18S - Silverstreak (Streak - dark grey deco)
2014 - MP-20 - Wheeljack
2014 - MP-21 - Bumblebee (Bumble)
2014 - MP-22 - Ultra Magnus
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2015 - MP-24 - Star Saber
2015 - MP-21G - Goldbug (G2 Bumble)
2015 - MP-12 - Sideswipe (Lambor - reissue first release)
2015 - MP-18B - Bluestreak (blue deco)
2015 - UW-02 - Unite Warriors Menasor
2015 - MP-25 - Tracks
2015 - UW-03 - Unite Warriors Guardian (Defensor)
2015 - MP-21R - Bumblebee Red Body (Bumble)
2015 - MP-14C - Clampdown
2015 - MP-26 - Road Rage
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2016 - MP-28 - Hot Rodimus (Hot Rod)
2016 - UW-05 - Unite Warriors Convoy Grand Prime
2016 - UW-06 - Unite Warriors Grand Galvatron
2016 - UW-07 - Unite Warriors Bruticus
2016 - UW-08 - Unite Warriors Computron
2016 - MP-14+ - Red Alert (Alert - anime deco)
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2017 - UM-EX - Unite Warriors Megatronia
2017 - MP-36 - Megatron (first release - anime deco)
2017 - MP-10B - Black Convoy
2017 - MP-37 - Artfire
2017 - MP-12+ - Sideswipe (Lambor - anime deco)
2017 - MP-39 - Sunstreaker
2017 - MP-15/16E - Cassettron/Cassettbot (4-pack - Wingthing, Enemy, Stripes, Nightstalker)
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2018 - MP-34S - Shadow Panther
2018 - MP-36+ - Megatron (toy deco)