Steamflogger Boss was printed in the set Future Sight , and the card alludes to the fact that riggers and contraptions may be part of the game in a coming set (the preceding 2 sets in the Time Spiral block were about the past and present).
However, seeing as there are still no mention of the assemble mechanic as of 2012, it is still primarily a joke card in the same vein as the Unhinged and Unglued sets.
While a 3/3 for 4 mana isn't terrible , it is definitely weak enough that it will only see actual play in limited decks that desperately need to fill up some mid-range creature slots.
Aaron Forsythe, the director of Research and Development for Magic: the Gathering, commented that the card was purely a joke and was probably a bad idea.
boardgames.stackexchange.com/users/191/Gordon Gustafson
Update:
It is now the future.
We now know what this mechanic is thanks to Unstable!
Contraptions aren't put into your main deck.
To play with them, you must build a separate Contraption deck In Constructed formats, such as Standard-but-with-silver-borders, Commander-but-with-silver-borders, and all-Un-set-Constructed-but-with-Steamflogger-Boss-I-guess, your Contraption deck contains at least fifteen unique Contraptions.
The Contraption deck is "singleton," meaning you're limited to only one of each Contraption.
In a Limited format, such as Booster Draft or Sealed Deck, your Contraption deck can contain any or all the Contraptions in your card pool.
The fifteen-card minimum and the one-of rule don't apply.
You can play whatever Contraptions you draft or open.
Several cards in the set will instruct you or a creature you control to assemble a Contraption.
To do this, turn the top card of your Contraption deck face up.
Then, put it onto the battlefield under one of your Contraption deck's three sprockets, helpfully labeled Sprocket 1, Sprocket 2, and Sprocket 3.
At the beginning of your upkeep, if you control at least one Contraption, you move the CRANK!
counter forward one sprocket (so, from 1 to 2, from 2 to 3, or from 3 to 1).
Then you can crank any of the Contraptions under that sprocket.
This causes their abilities to trigger.
You can put these abilities on the stack in any order.
Also, you don't have to crank a Contraption if you don't want to.
How you assemble your Contraptions determines what kind of infernal machine you're building.
Load up one sprocket to produce a devastating turn every three turns, or spread them out to make sure you get something every turn? Taken as a copy paste of the major points for the article detailing them here .
To all you still back in 2012, I hope this was helpful, you just have to wait 5 years or so to play with them.
boardgames.stackexchange.com/users/22380/Adam LeBlanc
Actually, there are other Riggers besides the Steamflogger Boss.
Moriok Rigger from Fifth Dawn had
the Rigger Sub-Type retroactively added to it after the Grand Creature Type Update.
Any Changling is also a Rigger, as well as the Mistform Ultimus
boardgames.stackexchange.com/users/1873/user1873
Read the ruling at the page you linked: Contraption is a new artifact type.
There are currently no artifacts with this type.
And there's no current game meaning of "assemble."
Wizards had a bit of "fun" with Future Sight, creating weird card such as this one, Dryad Arbor , Ghostfire , etc.
boardgames.stackexchange.com/users/2880/ikegami
Yes, Contraptions are (at time of writing) a joke, but let's not forget that a Steamflogger Boss does buff other Steamflogger Bosses (without even mentioning the many, many other Riggers that exist in the game of Magic, most of which are admittedly Changelings).
Your first Steamflogger Boss may just be a Hill Giant, but your second is a 4/3 haste, and by the time the third hits the table, you have three hasty 5/3 bad boys on your team.
Okay, maybe this scenario isn't exactly the pinnacle of brokenness, but it it goes to show that Steamflogger Boss's (first) ability isn't quite useless.
You could do worse for a cost of 3R...
boardgames.stackexchange.com/users/436/thesunneversets
Future Sight was a set full of "what ifs" - glimpses into possible futures for the game, and this was one of them.
Some of them were simply gags, and this was one of them.
(Although it's worth mentioning that new sets are starting to use terminology in the manner of assemble - detain, for instance)
boardgames.stackexchange.com/users/916/Allen Gould
I just saw this card called  Steamflogger Boss  today, but I've never heard of a Rigger, a Contraption, or an ability called 'assemble' in Magic. Am I missing something? Does this card refer to a very rare card type  like locus  of which there are only a few examples? It seems like the card would make perfect sense if I could only find something that could assemble a darn contraption...
What are Riggers and Contraptions in MTG and how do I assmble them? (Steamflogger boss question)
boardgames.stackexchange.com
<magic-the-gathering><mtg-joke-cards>
boardgames.stackexchange.com/questions/8354
boardgames.stackexchange.com/users/191/Gordon Gustafson
Steamflogger Boss was printed in the Future Sight set and alludes to riggers and contraptions in a future set. They aren't put in your main deck. Future Sight was a set full of glimpses into possible futures for the game, and the card alludes to the fact that riggers and contraptions may be part of the game in a coming set. With the Contraption deck you're limited to only one of each Contraption.  Contraptions aren't put into your main deck: To play with them, you need to build a separate Contraption deck  In Constructed formats and your Contraption deck contains at least fifteen unique Contraptions.
Future Sight was a set full of glimpses into possible futures for the game, and the card alludes to the fact that riggers and contraptions may be part of the game in a coming set  With the Contraption deck you're limited to only one of each Contraption.  Contraptions aren't put into your main deck: To play with them, you need to build a separate Contraption deck  In Constructed formats and your Contraption deck contains at least fifteen unique Contraptions. S0: Actually, there are other Riggers besides the Steamflogger Boss.   