On the issue of the bells for all of the tassels. On the Stewart piece, they are depicted as VERY narrow compared to modern ones. This is where I end up 'taking a leap'. The bells are so tiny in the images that they convey basically no detail at all (apart from general size and shape). I have a feeling that they probably AREN'T devoid of detail, but my guess is that they aren't Victorian in their level of detail either.

I am really on the fence on the issue of casting these versus building them up and doing a little hand stamped detail.
The owner of my local highland dress shop has two boxes of old (mainly Victorian) sporran bells that he uses on new and refurbished sporrans. Some are cast and others are constructed. Most appear to be silver plated. Almost all have molded or engraved details such as thistles and geometric designs. They are almost all much narrower than modern bells and the holes through which the chain passes are generally much smaller than modern ones. The chain must have been much thinner on Victorian sporrans.

PM me if you would like me to measure a few of them or ask the owner if I can photograph some of them or even see if he is willing to sell some of the one-off designs as patterns.