As for the blue trailed vase, it is the one that was discussed on here a few years ago. The seller, bakedbeans, who I had the pleasure of buying it from sent me the link to the thread. He had taken it to Elizabeth and Timothy, who thought it was made at the end of Michael's time at Mdina.
Now, I in no way want to contradict what any of them said but... I find this too interesting not to mention. Ron Wheeler was of the opinion that these were trial pieces for the attenuated bottles, which he said MH found very challenging and frustrating to make. Having seen a few more of these trailed vases, I'm now inclined to agree with Ron, as I often find myself doing on most things (he thought the SH vase was questionable, suggesting I post it on here for a definitive answer). Anyway, the ones I have seen, (including John's I think from the IOW archive) all show a definite progression of skill. It's almost like you can see Michael learning as he goes until he achieves a very high level of finish. At which point, maybe, he felt he was ready to make the trailed attenuated bottles.
Just a thought which may not be right, but as I say the examples I've seen (6 of them including mine and the one in the IOW museum) do definitely show an increasing level of finesse and quality of finish.