It's an alternative MacTavish one, one that hasn't been recognised by the chief methinks. My kilt maker has it's number as 1439 and this blurb:

Thompson/Thomson/MacTavish

Source: MacKinlay from Bannockburn Collect'n James Mackinlay a tartan collector between 1930s -1950s ,he hand coloured tartan stripes, this collection is in the Scottish Tartans Society archive.
It's a rare one that had to be specially woven but I really like it.