Given those dates and in those conditions, the half-crown coins don't appear to carry any premium value as collector coins, IMHO. However, the 1878 and 1915 are 92.5% silver and have .4205 asw each; the 1922, 1923 and 1943 are 50% silver and have .2273 asw each. (The 1955 is a copper-nickel coin without particular collector value.) So you've got 1.5229 ounces of silver melt value, or just above $57 at the moment. Hope that helps -- somebody correct me if you see any value above melt here....
Edited to add: Wybrit is right about silver wearing off a bit -- you'd expect to sell these at a discount from full melt value I should think.
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With one thing and another, an offer in the range of fifty dollars from an interested B&M dealer would be fair for the lot. (Yes, I know, below nominal 'melt').
Comments
Coins dated 1920-1946 are .500 fine and and contain .2273 oz of silver
Coins prior to 1920 are .925 fine and contain .4205 oz of silver.
Of course, the coins are quite worn so have lost some of their silver.
The 1955 Halfcrown is base metal - Nickel-Copper alloy, and is just a standard junk box item.
Edited to add: Wybrit is right about silver wearing off a bit -- you'd expect to sell these at a discount from full melt value I should think.