rigpimp, the original capsules for the KM 54 and 254 were made with nickel-foil diaphragms. By the time Neumann discontinued the KM 50 series at the end of the 1960s, they had already introduced their "linear admittance" K 64 capsule, which has been their stock in trade ever since; it was used in the KM 64 and U 64 (both from 1964), then the KM 74, KM 84, KM 140, KM 184, and finally the KK 184 of the current KM A/KM D series. This capsule type featured a new, grooved backplate design that greatly improved its off-axis linearity--and as with all but one of Neumann's microphone models from the late 1950s until 2000, it used a gold-sputtered Mylar membrane. (I'm attaching the page from Gotham Audio's brochure about the U 64 that lauds this new capsule.)
I mention this because your microphones don't have original K 54 capsules, but rather this latter type of capsule, attached via a retrofit kit ("KA 32/3-54") that Neumann offered once they ran out of the original type. The KM 54 was Neumann's first microphone to sell in the tens of thousands, and since nickel foil is very delicate, K 54 capsules needed replacing rather frequently. A strong gust of wind, or some bozo blowing into the mike to see whether it was "on" or not, could destroy them. Once Neumann stopped making those capsules, they soon ran out of them as replacement parts, but there were still many, many KM 54s in the field. So they came up with a kit that allowed a K 64 to be grafted onto KM 54 (and 254) microphones. The result is what you show in your photo. Most KM 54 and 254 microphones that you see on eBay also have this kit installed. For comparison, I'm also attaching a photo of a stock KM 54; it doesn't have the large, "RF-proof" Tuchel connector of the 254, but it has the original capsule head.
Since with this type of microphone the capsule determines far more of the sound quality and other acoustical properties (e.g. polar response) than its electronics do, your microphones are sonically much closer to the KM 64 (which was also AC 701k-based) and KM 84 than they would be to a KM 54 or 254 that has an original capsule. Again for comparison, attached are the response curves of the KM 54/254 with its original capsule; the on-axis high-frequency response rises quite a bit more, and the polar diagrams aren't as uniform across the frequency range.
--best regards
P.S.: Re-reading the U 64 text after a number of years, I see that Stephen Temmer (obviously the author--his pomposity is unmistakable) missed a few things, and not just the spelling of "synonymous". Number one, the acoustical delay ("phase shift") is not directly behind the membrane assembly; rather, it is situated behind the capacitive backplate of the capsule. Number two, a pure cosine function would yield a figure-8 pattern! Cardioid response is defined by (1 + cos theta) / 2 -- expressing the fact that a cardioid is the superposition of one-half omni (= 1, since the response is unity regardless of the arrival angle) and one-half figure-8 (= cos theta). -- Mr. Temmer was extremely picky and contentious, often writing letters to the editors of various audio publications to dispute points which were at times quite minor. I'm sure he would be appalled at getting called out like this, but tough luck, Mr. T.