The early ejection seats were simply bailout assists. Even after features like automatic seat separation were added, a survivable ejection had to be initiated at least 500 feet above the ground, much more if the airplane had a high sink rate. Ejection during takeoff or final approach was not an option.
Martin-Baker was dedicated to improving the seat capability and in the mid-fifties succeeded in qualifying a seat system that resulted from a survivable ejection on the runway at speeds above 100 knots. In 1956, BuAer contracted with Grumman to install the new Mk4 M-B seat in an F9F-8T for a demonstration. Flying Officer Sidney Hughes, RAF, successfully ejected from it at Patuxent River in August 1957 while on the runway at 120 kts.
This successful demonstration resulted in a Navy contract with Martin-Baker for the Mk5 seat, which was a strengthened version of the Mk 4 from a crashworthiness standpoint. (An actuator loop was also added at the front of the seat pan to expedite ejection if required, such as an emergency during catapult launch, or when g-levels made reaching the face-curtain loops difficult.) Most in-service Navy fighters with ejection seats were changed over to the new seat, either in production or as a retrofit. It took a few years because each installation had to be developed and certified by Martin-Baker. The seats were somewhat tailored to each aircraft type and therefore identified by a prefix letter, e.g. H5 for the F4H, F5 for the F8U, and P5 for the F4D (shown here).
The changeover appears to have begun with the single and two-seat F9F Cougars in the training command. The first F9F-8T ejection on Martin-Baker seats was in September 1958. The first Cougar ejection was in November.
Martin-Baker seats were installed in F3H BuNos 146709-146740 at the factory. The first ejections using a Martin-Baker seat from the F3H reportedly occurred in March 1958 with the last in a McDonnell seat in November 1960.
The F-4 Phantom first flew with a McDonnell seat but it was quickly supplanted by the M-B Mk 5 seat in production, probably in 1960 with the second block of production airplanes. (For more detail on the change to Martin-Baker seats in general and the F4H in particular, see http://phantomphacts.blogspot.fr/2013/10/f4h-phantom-ii-ejection-seat-history.html.)
Vought was reluctant to admit that the M-B seat was better than its own (although they did install a M-B seat in the third F8U-3 which flew in late 1958). Its seat was a modification of the Douglas Escapac seat which also provided survivable ejection on takeoff and approach. However resistance was futile. M-B Mk-F5s were installed in F8U-2s toward the end of their production run and retrofitted to surviving F8Us. (Contrary to some reports, a cockpit console width change was not required, only different rails and catapult fittings plus stiffening of the bulkhead; M-B assembled the F5 with a narrower seat pan.)
LTjg John T. Kryway cut it a bit fine with the M-B seat but survived after his hard landing on FDR in October 1961 necessitated jettisoning his F8U-1:
The North American FJ-4s appear to have begun to be switched over in early 1961 at the first or second major overhaul after late 1960. The first reported ejection using the Martin-Baker seat was in September 1961. If you don't have a photo of the specific aircraft being modeled, the best bet is the original seat. The earliest example that I found of a MB seat in the FJ-4 is VA-144's 3rd deployment, November 1961 to May 1962. However, there is a picture of a reserve FJ-4B dated July 1963 with the original seat.
No M-B seats appear to have been installed in F4Ds during production at Douglas, but most survivors were eventually converted to the Mk-P5 during an overhaul.
One notable exception to the changeout to M-Bs was the F11F Tiger. A quantity of 201 seats was procured for the Tigers but they were not installed, with the exception of two F11Fs subsequently pulled out of long-term storage for an in-flight thrust reverser program.
Martin-Baker demonstrated its zero-zero seat in 1961, with the Navy procuring it in 1965 as the Mk7. The performance increase was accomplished by the addition of a rocket.
The Mk5 and Mk7 seats are easily differentiated by the parachute housing. On the Mk5, the
parachute was enclosed in a horseshoe-shaped fabric casing that was housed in a black-painted metal shell on the upper seat back. On the Mk7, the parachute was enclosed in a green composite horseshoe-shaped shell mounted on the upper seat back.
There were however, many detail differences in the headrests, ejection-initiation handles, seat cushions, straps, among the seats installed in different aircraft, services, and countries. For example, the Martin-Baker seat in a U.S. Navy F-4 was not identical to the one in a U.S. Air Force F-4. The one in the British Phantoms (the right one in the illustration above) was a third configuration.
The changeover to the Mk 7 seat in U.S. Navy fighters began in late 1967 or early 1968 with Mk 5 seats being modified to the Mk 7 configuration. The first F-4Js were produced with Mk 5 seats (deliveries with Mk7s reportedly began in December 1967) and then retrofitted, as were F-4Bs; the changeover was reportedly complete by 1970. (The last RF-4Bs were reportedly delivered with the Mk 7.) The F-8J conversions from F-8Es included the installation of the F7 seat. The Hs (rebuilt F-8Ds) after mid 1968, and all Ks (rebuilt F-8Cs) and Ls (rebuilt F-8Bs) models were also delivered with the F7 seat.