It's a Parade king. The badge puts it a '56 -'59. Neither head is original to the drum, although they are both calf heads. The strainer points to earlier rather than later, but might not be true with a marching drum. Slingerland started stamping the date inside the shell in '58 or so, so pull a head and check for a date stamp, if there isn't one then it's a '56-'57, and if there is one, it will say when it was made.

I pulled the head and there is definitely no date stamp, so I guess we'll go with 1956-57. I'm curious as to why you think the bottom calfskin head is NOT original to the drum. It looks very very old and bears the stamp:
"Coast Select TRANSPARENT CALF, NATIONAL RAWHIDE MFG CO Chicago, Ill, PROFESSIONAL QUALITY"

Thanks so much for taking the time to respond to my query!

Glad to help. Slingerland only installed Slingerland branded heads. The top one is a Ludwig head. The bottom is a National Rawhide Company head. National Rawhide, or NARACO, as they were also known, was the largest aftermarket supplier of calf heads. I believe they were the OEM for heads for some of the smaller drum brands, but Ludwig and Slingerland always made their own heads.

+1 with the info you have received so far.  It's possible the date could be narrowed further if you post a picture of the interior showing the lug fasteners.  Also, any white grease pencil markings on the interior?