What you're REALLY looking for is a value for both rifles isn't it? Just look at past gunbroker or similar auction sites and identify wrapped rifles that have been sold and that'll give you some idea. But they are getting fewer and fewer every year.

As for the unwrapped rifle, you only have the sellers word that it's fired 20 rounds and unless you are an experienced barrel viewer (and very few of us are.......) then the average enthusiastic amateur, even with the Armourers gauges, would be hard pushed to tell the difference between 20 and 2,000 rounds approx. (this is in what Armourers call its 'first quarter of life'). It is just an extremely good condition used rifle. On the other hand, you KNOW that the sealed one has only fired one (or two) proof rounds. Just my 2c's worth