There are Five types of mystery boxes in the game Bronze, Silver, Gold, Platium or Diamond(Platium and Diamond were added at a later date).
Mystery boxes (crates) are available in the store (the Diamond was removed from the store and will only be offered in special deals), you can either get consumables, equipment or weapons.
Chances vary depending on the box.
The drop chances can be found on the Mystery Box Drop Rate section of the official website (which is now outdated).
Mystery Boxes where updated over time, see images below for more information.
Mystery Box update: 27-08-2013
"Just in time for the new tier system, Mystery boxes are getting upgraded too. Now Mystery boxes no longer drop standard weapon or armor variants, but special-edition variants only, which means you can use every item you receive in a Mystery box instantly.
Now that all Mystery boxes are more valuable, Bronze Mystery boxes will increase in price, while Gold and Silver Mystery boxes now cost 25-30% less GC."
Mystery Box update: 15-08-2014
"MYSTERY BOX UPDATE
Coming soon in update 1.2.2 GRP is improving all Mystery Boxes to offer better items for everyone! Now each Mystery box is less likely to award attachments or consumables and more likely to give you guns and gear.
Now with every Mystery Box you have the chance to score top-tier gear and legendary weapons from Assassin’s Creed, Arctic and Jungle up to the powerful and unique AK-200 series."
Mystery Box update: 16-09-2014
"NEW DIAMOND AND PLATINUM MYSTERY BOXES
This Wednesday we’re unveiling two new Mystery Boxes with higher chances to win greater rewards: Diamond and Platinum. Both boxes offer higher odds than any other at receiving top-tier limited edition content as well as legendary items.
Diamond and Platinum Mystery Boxes have the best odds of containing a legendary item such as an AK200 or potentially one of two legendary Tactical Suits: Ballistic or Ultra-light.
Check out all the details on your drop chances and stats for all legendary items below."
Note that "equipment" includes headgear which have no in-game benefit and are purely aesthetic. In addition, these items have no re-sell value making them both the most likely product of a diamond mystery box as well as the most useless and expensive.
OLDER/OUT-DATED INFORMATION BELOW
|Item Given||Number Of Times||Odds|
|MSR SD OPM||1|
|AFC-S300 Helmet OPM||1|
|BAT-G2M Helmet OPM||1|
|BLCV-LE HOOD OPM||1|
|Model 10a C OPM||1|
|Hermes R-03 MK2 OPM||1|
|Hermes R-04 Mk.III OPM||1|
|Gold Inserts (Given in multiples of 6)||4|
|Number Of Times||Odds|
|ECW-G5 RS Hood ALP||1|
|TITAN R-04 Mk.IV ACU||1|
|MP7 SD TRT||1|
|MP9 SD JGL||1|
|MK16 CQC ALP||1|
|CBRN-L4 Headgear ALP||2|
|M500 C JGL||1|
|M249 Para JGL||1|
|SVD-H SV Black||1|