Very little information has been brought to light regarding the APH-7 helmet. It looks just like an APH-6 helmet equipped with a strap suspension assembly and adjustable neck strap instead of the standard fitting pads. The APH-7 is mentioned in a 1963 US Navy report from a helmet design symposium. The report criticizes both APH-5 and APH-6 for being too uncomfortable due to heat build-up and it mentions that a return to a strap suspension assembly would solve that problem.  It therefore indirectly transpires (no pun intended) from the report that the APH-7 was designed as a cooler alternative to the APH-6.

APH-7 helmet manufactured by Gentex. Apart from the strap suspension assembly and the externally adjustable
nape strap it looks just like an APH-6A helmet. Pictures © DocBoink.

Information about the DH-71 helmet is even more scarce than is the case with the APH-7 but it seems to be a precursor to the APH-7 helmet. It looks like an early APH-6 helmet but it also has a strap suspension assembly and an externally adjustable nape strap.

DH-71 helmet made by Gentex. This particular helmet is not typical since it has USAF standard communications and CRU-8/P oxygen connector even if the navy wing has been retained on the visor housing. It belonged to a USN LCDR who possibly was an exchange pilot with the USAF or flew an aircraft type that had USAF com requirements. The visor locking assembly in third picture from the left is also unusual. Pictures © Milehigh.

Comparison between DH-71 and APH-7. The two pictures to the left are external views of the two types of helmet
types from the outside. DH-71 to the left and APH-7 to the right. The two last pictures illustrate the differences in
the strap suspension assemblies between DH-71 (left) and APH-7 (right). Pictures © Milehigh.

APH-7 helmet with original squadron artwork. Without a picture of the helmet actually in use, it is almost impossible
to nail down the squadron based on the lightning bolts alone. The bolts are featured in innumerous squadron patches. All pictures are thumbnails. Pictures © kevyjoe

APH-7 helmet with original diamond artwork. It is not clear whether the helmet was used in VF-102 Diamondbacks
or if it is just a fantasy pattern. Pictures © Figmo

APH-7 with one-piece ramshorn dual visor. The visor is definitely a retrofit since the helmet itself was made by Gentex
(see label to the far left) and the one-piece ramshorn visor was made by Sierra Engineering Co. Pictures © kevyjoe

Far left and left: Another double-visor APH-7 helmet, here with original VF-111 'Sundowners' artwork. This helmet is
on display at the Naval Aviation Museum in Pensacola. Pictures © Shark. Right and Far right: APH-7 helmet with stars
on the visor cover. Pictures © Trey Turner

Another example of the DH-71 helmet. It differs from Milehigh's example by having a visor housing of later design
and civilian standard communications. It is marked "USAF Capt. Dillard" on the rear but according to Capt. Dillard's
family he was never a pilot or aircrew. The lettering may have been applied for fun only.
Pictures © idnavywife

APH-7 helmet used by the CAG from Carrier Air Wing 21. Pictures © unknown