Re: 1939 National Register
FindMyPast gives an RG101 reference: e.g. RG101 6303C-020-18 RJIF, which is piece, page and line number. I tend to use FMP instead of Ancestry for searching the 1939 register because of this.
A note on the birth dates given, however, as they are frequently wrong. Always cross check with the online GRO index. I have had several instances where the year is incorrect, and one or two with completely wrong dates.
From: firstname.lastname@example.org [mailto:email@example.com] On Behalf Of John Liddle, Backwell, North Somerset - "Where the cider apples grow" via groups.io
Sent: 14 January 2021 11:34
Subject: Re: [family-historian] 1939 National Register
I think you're being a little unfair - most providers have their own internal file reference structure for the data they provide and the TNA referencing system may not play nicely with that.