Midland Railway Three-Wire Three-Position block instruments
The Midland railway also manufactured their early instruments out
of old telegraph instruments, resulting in the instruments looking very similar
to those of the Great Northern.
The significant difference was the latching mechanism for the commutator, which was a more difficult sliding latch (just visible on the right-hand instrument) necessitating a knack to be learnt to operate the block efficiently.
The instrument on the left is a non-pegger, but the telegraph handle was retained to allow the block needle to be momentarily deflected to indicate train routing information. However, this feature fell out of use in LMS days (being replaced by routing bell signals) and was disconnected.
These examples were found at West Hampstead, more details of which can be found in the Photo Gallery.