Trying to make sense of some old blues discographies and to make a difference between different recordings of the same song later on, I am looking for a place to enter the master numbers.
For example, Mississippi John Hurt. Let’s take his first 10" shellac record:
On the label, you can see 8560, which is the release catalog number.
But below the title and artist, there is 400221. That’s the master number. (Recordings were done, I believe, on one-sided 10" records, and got a number. Often also a take, this particular one is 400221-B (second take) although the B is not present on the label.
On recordings, it’s good to add the matrix numbers in the disambiguation, especially when there is more than one recording of a work by the same artist. You can add to disambiguation or annotation, but there is nowhere else unfortunately for the info. What I usually do, is make sure the first release of the country of artist (on old blues, mostly US), is added as a single, then merge all from comps, into that one, with the disambiguation on merged recording. Also, on MB, different masters aren’t separate recordings, so please do not add another recording that represents that.
It might be good to have a structured field for master/matrix number, but with what we have I do what @tigerman325 does and add it in the disambiguation.
By “master records” you mean record company files etc.? We don’t really have a place for those in MB, although we of course have relationships for a lot of the data recorded in those (recording date, location, personnel etc.)
I think the “W” may indicate it was electrically recorded. (See http://early78s.uk/markings-on-78-rpm-records/ ) A lot of record companies applied prefixes to matrix numbers indicating something about how or where they were recorded, but generally those prefixes are not required to uniquely identify the recording. For that reason they get dropped from some discographies.