Masters Edition IV

Clockwork Swarm

Clockwork Swarm enters the battlefield with four +1/+0 counters on it.
Clockwork Swarm can't be blocked by Walls.
At end of combat, if Clockwork Swarm attacked or blocked this combat, remove a +1/+0 counter from it.
{X}, {T}: Put up to X +1/+0 counters on Clockwork Swarm. This ability can't cause the total number of +1/+0 counters on Clockwork Swarm to be greater than four. Activate this ability only during your upkeep.

Clockwork Swarm enters with four +1/+0 counters on it.
Clockwork Swarm can't be blocked by Walls.
At end of combat, if Clockwork Swarm attacked or blocked this combat, remove a +1/+0 counter from it.
{X}, {T}: Put up to X +1/+0 counters on Clockwork Swarm. This ability can't cause the total number of +1/+0 counters on Clockwork Swarm to be greater than four. Activate only during your upkeep.

Homelands

Cannot be blocked by walls.
When Clockwork Swarm comes into play, put four +1/+0 counters on it. At the end of any combat in which Clockwork Swarm attacked or blocked, remove one of these counters.
o
X, oc
T: Put X +1/+0 counters on Clockwork Swarm. You may have no more than four of these counters on Clockwork Swarm. Use this ability only during your upkeep.