hi looettes and welcome to the forum.
i don't know for sure how much your mk2 is worth... and quite frankly my track record in this department isn't good but they do go for a lot of money especially with all 3 barrels.
post some links to photos, or email some photos to me (email in profile) i'll upload them to my bit of webspace then post links here for all to see, you will get a better response if folk can see the item they are helping to value...