It seems many production processes were used during the mint mark tun 1636-8. The sequence relating to the portrait type is probably not definate, but if considering the likes of Sharp E1-5 the relative relation to the pre-prior designs it must be close to what the issue order was. As said above the early 'tun' coins seemed to be carried over from ealier portrait/mint mark issues as seen in the E1/E2 bust which are evident in 'D' seires coins, and likewise the latter E5 (and a recently discovered E6) portraits which were later carried over under the F1 and F2 coin with inner circle, coins which give further evidence to the relation to the Aberystwyth mint which used the Tower F2, F3 and F6 designs.....A very busy couple of years!!