I shoot hammer guns and am always buying and selling them.
A Watson in good to very good condition would bring about $2,000 but that would be with no cracks, rust and minimal patina.
The benchmark I normally go to are my Westley Richards and Thomas Bland and Sons.
These two guns - a 10 gauge bar in wood ( W.R.) and a smokeless proofed 20 gauge ( Bland) are is super shooting shape, cased, and the bland is lettered.
Both are pre 1900 and both were right around $2,000.The barrels on both guns are excellent .
Fro the pictures yours is nice Speckle, but as Mooncoon and the others have sated, it would be a tough sell for $450.
As a collector it's not desirable, and as a shooter the crack will have to be repaired and the barrells and locks checked before that happens.
Cat