1998 1c Double Indents With Partial Collar?

@coin, what is the diameter of the non-double struck region?

That's quite interesting. The diameter for the outer part seems fine for a cent indent, but the bit toward the center seems to have too small a diameter. Almost looks like the coin was indented by a double struck coin that was about 90% off.

Hmmm... Looks like there are secondary design elements above IGWT as well.

How about this scenario:
-the planchet is struck normally but is not fully ejected and ends up on the collar.
-the next planchet can't seat properly and ends up on the bottom of this coin which is resting on the collar
-the next strike places the indent, the secondary design elements, and the partial collar on this coin.

(It seems like the secondary design elements would be most evident where the pressure was the lowest during the second strike.)

Just a thought.

This is a strange looking one, What could have caused that huge circular indent without bulging out the reverse?

It's very common for the radius of an indent or partial brockage to be much smaller than that of the coin. The pressure of the strike stretches out the struck tab.