@sforrest I just remembered having consulted the Yōgaku bunko's catalogue a while ago -- and now found that it's even available online: https://t.co/ayQ44eZOl3
So 文庫08 A0337 translates to:
文庫08 = 洋学文庫
A = 大槻家旧蔵
0337 = item no. (cf. p. 17 in the catalogue)