Combined waste and overflows weren't around then. Baths were cast iron, wastes were chunky brass, lead washer, boss white and a huge nut to fettle with footprints. Bath overflows went out the wall, and internal installations were capped off where outside wall was unavailable.The old penny was ideal for the job.
An old cast iron bath with external copper pipe, yes that could allow a spider entry, but they have surely got to be a minority now.