Writing the new Scottish book has unlocked many secrets. Not through extra reasearch, for the most part. But through combining information I'd already collected.
Admittedly, for one of the most revealing, I did take a second look at brewing records. Directly comparing the mashing schemes of multiple breweries was very revealing. Especially as to how prevalent the underlet mashing technique was. I wasn't especting that.
I've just put together the first set of Maclay recipes for the book. From 1909. I tell a lie, I had already done a couple from the 1930's. The later Maclay records in the Scottish Brewing Archive look more like someone's personal notebook than official records. They're in small notebooks with cardboard covers and lined pages. While those from 1909 are in a properly bound pre-printed ledger.
The 1909 book is in what I call English format. With each brew getting a whole page. Most Scottish breweries went with the one line per brew, across two pages, system. They're fairly well detailed, unlike the later notebooks. Which is how I know Maclay was another Scottish brewery to underlet mash.
Another thing I noticed. An early example of a new type of Scottish beer. A Strong Ale that, rather than being a type of Mild Ale, was a super-strength Pale Ale. Like this example from Maclay, which was parti-gyled with a 54/- Pale Ale. After WW I, this was the type of Strong Ale most Scottish breweries made. Other than William Younger. Who always were different.