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The Flatgate serial number 4330 would have been shipped in 1954. It would be considered a "Type 2" Flatgate. One question you didn't answer that makes a big difference in value. Has it been converted to where it now has the safety transfer bar? If it has been converted & the original parts are not with it,, that hurts the value.
Next, it's all about condition. An early gun like that can be considered a collectable one, but only if in very good condition. You mentioned it was very nice, but proper grading of condition is paramount for a gun like this. As such, it can be worth from $400 to around $600-$700. If they have the box & any paperwork, that adds to the value.
The Blackhawk 357 was made in 1970, and unless there is something unusual about it, around the $500 mark in value. Again, condition is important, but that late of a production model has to have something unusual to make the value jump.