I don't have the answer but I have a B17 and a B15 on my desk now...B15 was bought new in early 1950s, and a B17 on a Hetchins.
B17 - XUV that's all - oval badge.
B15 - A10 and ZOB1 - oval badge, the O could be a U or V.
I know for certain the B15 was bought new around 1951 (my Dad bought it).
The B17 is an old one but actual date purchased is unknown.
Both have bag loops.
Co-founder of a V-CC section, member South Eastern Road Club and owner of - 2005 Bianchi Reparto Corse (modern), 1985 Raleigh SBDU Pro Super, 1984 Raleigh LU Corsa, 1980 Allin Stan Butler Special, 1978 Ron Cooper, 2 x very ealry Roberts (late 60s/early 70s), 1975 Bill Philbrook tourer, 1966 Raleigh Superbe Roadster 1964 Allin Stan Butler Special Belgique, 1951 Hobbs of Barbican S/C, 1950 Hobbs of Barbican S/C, 1947 Hetchins Super Special, 1908 Centaur Featherweight.