Yes, the Silverstar are made from pure silver. They are very fast and bright fuses. So, if you feel they sound nice, they are definitely well broken in.
The Supreme fuses are much better, in my opinion. They are much smoother and don’t have that super bright "silver" edge. They will still have a very fast sound and may start to push the upper mids/highs too much in some systems. 60 hours is not a whole lot of time. I would say run it in for 100 or even 200+ hours before making a final decision.
The old Hi-Fi Tuning Gold were not that great of a fuse. They were warm sounding and at the same time had somewhat of a fast attack. The problem was they sounded somewhat metallic and had a really bad "glare" to them.
There is a new Hi-Fi Tuning "Supreme Cu". They use pure copper wire and end-caps, with the end-caps being gold plated. I suspect they will be a much warmer sounding fuse like the Isoclean, but better.