It is often said that “tight-open” assemblies (“gospel halls,” typically, in NA) have a heritage entirely distinct from the wider “Plymouth brethren movement,” and efforts are made to frame their history as independent, in origin and continuance, from those known under the broad designations as “open brethren” and “exclusive brethren.” See, for example, the brief history given by Norman Crawford: https://gospel.fromgravelhill.ca/assets/books/Norman-Crawford-Assembly-Truth.pdf
Now, definitely a certain frame of mind came with some of those mentioned in these histories, which ultimately crystallised in, (a) the Needed Truth cleavage, and (b) the oil-water separation of “open brethren” who practice closed vs. open communion.
Yet, the fundamental claim that “gospel halls” are a movement of God totally distinct from the pre-existing “Plymouth brethren” seems overly-simplistic in the light of historical evidence. For example, Ironside relates how Christians composing the newer group quite soon made contact with “open brethren” and began to fellowship with them, essentially combining the two in a little while: https://plymouthbrethren.org/article/5137
Looking at the advertisements in the back of early books published by John Ritchie, we find many authors who didn’t have their origins among these Scottish brethren, and in fact, predated them. It seems likely that, while certain distinctive convictions may have been arrived at apart from outside influence of the already well-established “brethren movement,” the further education of the Scottish brethren owed much to reading those who went before; and their establishment to essentially becoming grafted into the greater vine.
My hypothesis is: that while there may have been a fresh revival of concern about evangelism and assembling “after a scriptural manner” in 1850-60s Scotland, this group became almost immediately amalgamated with the pre-existing “open brethren,” instructed by the writings of both “open” and “exclusive” writers, and as such, is not to be thought of as a historical lineage entirely distinct from the wider “brethren movement.” I would happily have further evidence, to support or to the contrary, pointed out. Thank you.