I have one more proposal. If this is not correct, please open up again:
I found this text from some sort of an archive. It lists vehicles built with Grose body. May Grose be the answer?
NORTHAMPTONSHIRE RECORD OFFICE
Grose Holdings Ltd. (cont.) G
Photographs and Miscellaneous Items kept in Albums (cont.) Album 1 (cont.)
Photographs of Grose-built vehicle bodies upon other chassis (except where indicated) (cont.)
132 Buick 4 seater Coupe at Olympia (2 views). 1929
133 Vauxhall 4 seater Saloon at Olympia (2 views) 1929
134 Marquette 4 seater Coupe (2 views) 1929