Mystery on 1420

I added five new stations listening to my 0900 UTC top-of-hour recordings on Monday and Tuesday (using an ELAD FDM-S2 receiver and 80-meter inverted Vee antenna).

WBEC on 1420 kc in Pittsfield, MA, transmitting 1 kW, 59 miles to my north-northwest.

WKOX on 1430 kc in Everett, MA, transmitting 1 kW, 109 miles to my east-northeast.

WCEC on 1490 kc in Haverhill, MA, transmitting 1 kW, 123 miles to my northeast.

WQCP849 (Rhode Island DOT TIS) on 1630 kc in Newport, RI, transmitting 10 watts, 85 miles to my east.

And finally, the mystery station: WAAF on 1420 kc. WAAF, "Boston's Rock Station," is an FM-only station, but I heard it loud and clear on 1420 AM at 0900 UTC Monday. Was this a test or a pirate or what? 

Twenty-four hours later, WBSM (New Bedford, MA) dominated 1420, but there was a station that I could not ID playing rock music under WBSM. Driving to work two hours later, WLIS (Old Saybrook, CT) dominated 1420 on my Subaru's receiver, but again I could hear an unidentified rock station under WLIS.

I will listen again tomorrow morning.