while Holmes asks the lady about tramps in the area, there is visible on the wall behind electric cables mounted on the wall. this at a time when there was no electricity in Homes.
As Holmes goes to look upstairs after they find the bloody fingerprint , he passes 2 light switches on the wall with electric cable visible. At the time there was no electric lights as shown people still used paraffin lamps as the lady is shown holding it or candles ,
During Holmes and Watson's conversation with Mrs. McFarlane, the mic briefly comes into frame on the top right of the screen.
When Holmes is explaining the murder of the old sailor he produces what he calls a Great White shark tooth as evidence. The tooth actually belongs to a Sperm whale.