Late Use Of A Jack O' Lantern Cancel ?

Given the stamp issue, this usage would be on the late side, and my gut makes me question its authenticity as I ponder whether or not to pull the trigger on the 'buy button.' The part of the cds visible in duplex seems a bit questionable as well (not to mention, with a clear strike of the Jack O' Lantern as seen here, wouldn't one expect a better strike of the cds?).
Any opinions?

I don't see any wrong with the positioning. Killer on the stamp, CDS on the envelope, the way it is supposed to be, and the reason why duplexes were developed.
Whether it is intended by the maker to be a jack-o-lantern, man-in-the-moon, smiling face, mask, or similar is a matter of guessing. Without any vertical striping or a stem, I have a hard time classifying this as a jack-o-lantern.

Having specialized in jack o' lantern / pumpkin cancels for the last several years, I find the majority of them will have neither stripes nor stems (unlike the Waterbury version). A quick peek at one of my pages holding 35 examples, most with certs, has only two with stems and none with stripes. The same applies to tracings in Cole, Skinner, and Clark, amongst others. In fact, many cancels with stems (similar to the Appleton, Wisconsin apple) have been accused of being just that.

Edited to add: I'm aware of what duplex cancellations were designed to do, but that wasn't the question. I was wondering about the disparity between the intensity/clarity of the strike of the killer vs that of the cds.

Wow, after looking at the image and if I had to report a description to the police of what I saw, I would have to say a Ninja Turtle. Michaelangelo, or Donatello It truly is amazing how much that image looks like the Ninjas, but about 80 years earlier.

Just for the sake of 'closure,' with some help on the Frajola MB, turns out this is a Salkind HU-B0-2 Pumpkin cancel, possibly used at Newkirk, Oklahoma.