Similar to the Monastery Credits of Shing Jea Island, the mainland in Cantha has items that are given as quest rewards; these are Imperial Commendations.

Silver packages these Imperial Commendations are traded in to the Imperial Quartermasters that reside in Kaineng Center.

For one (1) Imperial Commendation you can receive:

• Identification kit
• Salvage kit
• Hunters Ale
• Scroll of Adventurers Insight
• Dye Remover

For three (3) Imperial Commendations you can receive:

• Forbidden Key
• Expert Salvage Kit
• Superior Identification Kit
• Rune of Holding
• Scroll of Rampagers Insight
• Scroll of Hunters Insight

For five (5) Imperial Commendations you can receive:

• Superior Salvage Kit
• Scroll of Heroe's Insight
• Scroll of Berserker's Insight
• Scroll of Slayer's Insight

Real's tip:

You may see people in towns offering to buy all of your Monastery Credits or Imperial Commendations, chances are that these people are aiming for the ‘drunkard' title (see Titles explained for further info).

I'd say make sure you trade a couple of the commendations in for Forbidden Keys.  The chests for these keys are located in the Raisu Palace Mission (2^nd last Canthan mission) and these chests are known for their high percentage of gold item drops with rare skins!