From Ron Salvatore:

The Micro Collection figures each have a six digit code stamped either
on the bottom of their bases or, if they don't stand on a base,
somewhere else on their bodies. The first three digits of this code
identify the set to which the figure belongs. For whatever reason,
most loose micro collectors aren't aware of this but its really quite
helpful.

Mail-Order Set (088)
088-001...Rebel
-002...Rebel
-003...Rebel
-005...Snowtrooper
-006...Snowtrooper
-007...Snowtrooper

Bespin Control Room (256)
-001....Luke shooting
-002...Luke falling
-003...Vader pointing
-004...Vader w/ saber

Bespin Gantry (258)
-001...Luke hanging
-002...Luke w/ saber
-003...Vader w/ hand out
-004...Vader w/ saber

Snowspeeder (261)
-015...Pilot
-016...gunner

Wamp Cave (269)
-001...Wampa
-002...Chewbacca
-003...Han
-004...Luke
probot (no number)

TIE Fighter (270)
-010...Pilot

Xwing Fighter (270)
-014...Pilot

Freeze Chamber (460)
-009...Han
-010...Han in Carbonite
-012...Lobot
-013...Vader
-014...Boba Fett
-015...Stormtrooper shooting
-016...Lando
-017...Stormtrooper standing

Turret Defense (463)
-010...Han
-011...Luke on Taun Taun
-012...Rebel Commander
-013...Rebel Soldier lying
-014...Rebel kneeling
-015...Rebel stepping forward

Death Star Compactor (517)
-014...Luke Stormtrooper
-015...Han ST
-016...Vader
-017...Ben
-018...Leia
-019...Stormtrooper shooting up
-020...ST shooting
-021 ST shot

DS Escape (583)
-018...Luke
-019....Chewie
-020...Vader
-021 Leia
-022...ST walking
-023 ST kneeling

Generator ATtack (668)
-001...Snowtrooper gun at hip
-002...Snowtrooper shot
-003...Snowtrooper crawling
-004...Snowtrooper gun on shoulder
-005...Snowtrooper kneeling
-006...Vader

Ion Cannon (692)
-001...Rebel Commander
-002...Soldier
-003...Soldier
-004...Soldier
-005....Soldier
-006...Han w/ Taun Taun
-007...Leia
-008...Luke

Millenium Falcon (733)
-001...Threepio
-002...Artoo
-003...Luke
-004...Han
-005...Lando
-006...Chewie