Hi, I have a copy of an RAF Historical Society Journal that has a series of articles about RFC & RAF bomb development, and the Type A trolley is briefly mentioned therein, as follows: Ancillary equipment
The introduction of bigger and heavier bombs sparked parallel developments in the context of ancillary equipment, such as the tractors and trolleys needed to transport them and the hoists that were needed in order to load them, all of which had to be done safely, of course. Prior to 1942 the Type A bomb trolley was in general use, although its maximum load was a mere 500lb. By that time, however, two additional models had already been produced: the Type B, which was capable of carrying four 500 pounders, and the Type D, which was particularly associated with the Wellington, Lancaster and Halifax and could handle a 4,000 lb HC bomb. With the increase in size and weight of bombs the Type C trolley was introduced with a maximum load of 6,000 lbs and the Type F which could deal with 8,000 lbs. The design and construction of these various trolleys was pretty much the same and they could all be used to carry virtually any types of bombs, so long as their weight limits were not exceeded.
It's available online at: https://www.rafmuseum.org.uk/research/default/raf-historical-society-journals.aspx (Journal 45, page 34 has the reference)