Not to detract from the superb 20th and 21st century examples here, which perhaps represent another zenith of the finest Barlows that have been made, I thought I would present this as a footnote for other students of slipjoint history.
I found this photo while researching another knife yesterday. The knife was uncovered in an archeological dig on the grounds of the Prebendal Manor in Nassington, near Peterborough in Northamptonshire, England. It dates back to the 17th century. The distinctive long bolster and curved stag handle are immediately recognisable. I don't know whether the blade would have originally been a spearpoint or sheepfoot. What do you think?
I particularly like the way the soup-bone like channel in the stag covers, organically follows the curve of the handle.
Unfortunately, I've not been able to find any more information on any possible provenance for this Barlow knife.
https://ehive.com/collections/4185/objects/92262/a-18-century-folding-knife-with-an-antler-handle
Something about it put me in mind of Charlie's 'Ol' Scratty', back in post 14362. (Hope you don't mind the repost, CC.)
The Manor site itself has a long and storied history, going back to Neolithic times - I'll leave these links here for those who are interested, so as not to divert from the thread.
http://www.prebendal-manor.co.uk/history.html
http://www.britainexpress.com/counties/northants/properties/prebendal-manor.htm