It is 1 1/8" steerer - length is dependant on the size of the frame.
Is that your green one? It is s Monatana I think - 501 Magnum. Very nice.
Catalogue spec for the UK was X-1 and flouro pink forks instead of yellow.
Yes the Green one is mine your right when i bought it second hand 94/95 it did have pink forks and i think the frame was pink yellow and maybe green. I had it resprayed a couple of years after buying it. the only other one ive seen is nevadasmiths. would love to see a picture of mine as it was id consider restoring it. Catalouge copy would be good. Id post more photos of it but im in middle east and the bikes in uk.
Welcome to the club Glenn! Pretty exclusive as there aren't many Nigel Dean MTBs on here - 3 including yours I think!
Here is a scan of a test on your Montana:
I also have the listing for it along with a black and white photo from the buyers guide in 1990. I will scan and post this tomorrow for you
I have seen one other Montana - it was on eBay US, no-one else bid but the seller wouldn't ship it
That one had a yellow frame, black forks and similar stickers to my Nevada.
As the article says you could have pretty much any colour you wanted.
'Standard' was the brown/sparkle and coloured forks, I remember a mate at school had a Montana, it was the same frame colour as mine with pink forks.