Tsuba Iron

I can see why Tsuba are a separate entity for collectors. This one is an iron tsuba - is iron used because it is cheaper than bronze or easier/harder to work or some other reason?
Is it possible to roughly date just by shape and design, when there is no signature present? Has this shape got a specific name? It is almost like a rounded, soft octagon. It is 70mm by 62mm by 3mm thickness. A dragon - not sure what it's doing?

How to you grade/rate tsuba? - is it always the one with more intricate design and use of gold/silver that is priced higher? Or are the intricate fretwork type more desirable?
Are there recognised 'smiths' who are famous (relatively) in the tsuba world?
These are probably very basic questions that could be answered by a good reference book or website.
Anyway, I chose to start here. My main interest is in their connection or not, to the blade. I expect many blades have had their fittings changed over the years but it seems that any that exist with their original mountings/fittings would be more desirable to collectors? How does one verify if this is the case or is it impossible? Ansd is it actually important?



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