I want to know the answer to the following question:
What was the first model of HRF (Height Range Finder) used by the British?
All the background I'm provided with is that "This led to the Height/Range Finder (HRF), the first model being the Barr & Stroud UB2, a 2-metre optical coincident rangefinder mounted on a tripod.". Is that enough to answer the question?