Schematic: Large Seaforium Charge

Source
This item is a World Drop, from creatures of approximately levels 34 to 40. While the bulk of the reports of its dropping are associated with mobs from the Scarlet Monastery instance, there are also large numbers of reports of creatures elsewhere dropping it. (The Scarlet Monastery reports may be more due to the reporting than the dropping.)

As with may other Engineering schematics, this has been reported to drop from Mekgineer Thermaplugg as well, about 0.2% of the time.