This does not look recast. It is a normal pattern piece with normal finish. At 25mm that is the upper limit of diameter for this pattern. A piece recast from a circulation brass coin would lose 1mm of diameter. What indicates it is not plated or washed?
Production casting would make about 60 pieces to a tree, but the mother cash were not attached to each other. It would have been at least possible to take an individual one to cast one or a few silver cash, in the shop which produced the cast mother cash. Or outside the mint. Chinese mother cash were not dumped into circulation after they were no longer needed, as happened in Korea and Japan. They were so carefully guarded that few can be found today certifiably genuine. It is not even known for certain what metal was used for them in the provinces, when they were generated locally.
Some background, mother cash were themselves cast at this point at all mints. At the central mints they were of brass, but the exact composition is not known. Properly, they should have been of a composition for clear casting detail and ability to be finely tooled. Traditionally, mother cash were cast in lead or tin. Master patterns were carved in tin. Charm patterns were sometimes carved from wood. The central mints produced greater quantities, thus needed more and more durable seed coins, and did not always produce them the same as smaller or private mints would. At one point they used ivory for master cash.
Any judgment about this piece would have to wait for alloy testing on the surface and interior. By far the most likely is a normal coin plated or washed.
