All castings produced in 2 halves, the pattern is doweled to ensure correct alignment in the foundry core boxes providing the core boxes are aligned properly, not easy with small castings not much room for error.
The secret of a good casting for small items is the mould mix, Fine Green Sand mixed with a fast curing adhesive gives a very good finish.
Generally I have found Stuart castings good, once the crust has been removed with a 1/32” first cut with sharp lathe tool about 300 rpm and No Lubricant then resharpen to finish.
My only criticism is that Stuart's should allow more material on their Castings for machining, Pattermakers allow for contraction on patterns.
Most problems come with machining valve chest covers being only 3/16” thick, and the crust can be quite thick.
If you have a problem with a particular casting Stuarts will replace free of charge.