An interesting and very informative overview. Your final remark reminds me of the regret voiced by Martin Folkes concerning the lack of records of this coinage in his time. He wrote: “It were to be wished that some account of it had been published whilst the memory of the transactions was yet fresh…..As it is only from very imperfect tradition that any knowledge has been handed down to us. ….Concerning all this money I should be very glad to be better informed.”
The lack of data doesn’t seem to hinder the compilers of the GB 200 Coin Index - “Tracking performance of the top 200 English coins”. With regards to the “Scarborough Broken Castle” Group, (the only siege issue covered). Of the dozen denominations listed, six are believed unique and mostly reside in museums, of four others only two examples each are thought extant, which leave half a dozen sixpences and a few shilling. I thought I would add this photograph of a Newark halfcrown 1646.