that's a Single-Locking trem, i.e. a bad piece of sh!t. that's not a 550 of course, looks more likely something like a pickguard-version of the 270 (indonesia/china).
the RG550 always sported the following trems:
EDGE
LO-PRO EDGE
anyway, there are some japanese-made cheapos, like the 250B, that sport bad trems like the TRS101, but i think that's not japanese. ask the seller to take a pic on what's written behind the headstock.