I can see why you're confused mate, the bottom barrel certainly appears to be marked '60' whilst the top appears as an '80' to me - might be best to write away for that one & verify the loads first.
I suppose you could still start at the 'tropical' level & see if it regulates there, the barrels will tell you what they like anyway.
Apart from that you have a gorgeous piece of history there mate; an amazing piece to say the least!
I do love the 450NE as 'the cartridge' for DG, but this is in my eyes a true working double, yes just a little fancy - but not over the top at all......bloody corker she is!!!
Done it again Buckstix - can't wait for the 'loads' to come out!
Cheers