细节
A large sliding caliper by Troughton & Simms,
with vernier inside and outside scales to 30 and 28in on brass arm and steel indexes, marked HW No. 92, in shaped wood case with outside slots for mounting the caliper in use
with vernier inside and outside scales to 30 and 28in on brass arm and steel indexes, marked HW No. 92, in shaped wood case with outside slots for mounting the caliper in use