In this paper we analyse 70 years of archival Harvard and Schmidt plate data of the 16.6 d Be X-ray binary A0538–66 in order to search for the presence of the long-term period of 420.82 \pm 0.79 d found in MACHO photometry ( Alcock et al .
2001 ) .
We find evidence for a long-term period of 421.29 \pm 0.95 d in the archival data , and examine its stability .
We also combine the archival and MACHO datasets in order to improve the accuracy of the orbital period determination , using a cycle-counting analysis to refine its value to 16.6460 \pm 0.0004 d. We also test the model proposed in our previous paper ( Alcock et al .
2001 ) with observations documented in the literature for A0538–66 from 1980–1995 , constraining the system inclination to be i > 74.9 \pm 6.5 ^ { \circ } .