I'm looking for info about the relationship in time and manufacturing between these two Hemi 106 [250]s. Notice the pronounced flared skirt on the right hand insulator; straight skirt on the left. The left hand (straight skirt) mold appears to be identical - except for the drip points - of the SB 106 in the accompanying photograph. Does that imply that the straight skirt was produced before the flared skirt? Covington or Muncie?