Technically, yes. Rounded corner is just a nice way of saying a piece of the corner is missing. The catalog prices in Scott are for VF stamps free of faults. The higher the catalog price, the greater the hit the retail value takes.
Nevertheless, I still like your stamp!

While many collectors like to get hold of that "perfect" stamp, I think your stamp has character -- a battle-experienced veteran with the medal (i.e., postmark) and the scars to show for it. There is value in a stamp far beyond the quantification efforts of catalog prices.
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2) I notice several types in the Scott catalog which one is this?
In the Scott catalog, Malta #8(1Jan1885) -- the one half penny green.

k