With the unevenness of the lines, and smeared ink under the apex of the angle (I used that twice today!), looks like a pen cancellation to me, maybe a revenue usage?
The only thing is, Michael, there is a partial CDS that looks like a postal cancel; it would not have both a postal and fiscal cancel. I wonder if Arno's correct, that maybe this was part of a larger package, where the CDS appears on some stamps and someone further canceled the others. The 5R value tells me this was not a letter but was likely part of a parcel.
Still, I've not seen such a symmetrical angled cancel before; usually they just mark roughly over all the uncanceled stamps.