Daryl, I have a Henry Clark Case Labelwhich shows both the 38 Gallowtree Gate, and 20 Humberstone Gate, address. It pictures an impressive double fronted shop with a side entrance to the Midland Gun Works.
Clarke also also states on the label;" Patronised by the Prince of Wales". Likely because the prince purchased cartridges to use at the shoots held in nearby Bradgate Park. The bags at these shoots ran into the thousands and attracted large crowds to see the prince shoot.

Roy Hebbes