Measure resistance between terminals labelled '1' and '15'. Should be less than 0.5 Ohm. Resistance between terminal '1' and HT output as well as terminal '15' and HT output should be around 10-12 KOhm. That's no proof that coil is okay but rules out some types of failure.
Unfortunately there is no easy on the bench way to confirm operation of an HT coil without some proper testing kit. Coils do degrade with time through insulation breakdown. If you have any reason to doubt an aged coil then a new replacement is the best course of action. Beware of Chinese made coils. They really are garbage.