By the end of 1937 some 2000 sets had been sold.
A year later, only 200,000 sets had been sold of an expected million.
By 1977, more than 200 sets of plans had been sold.
About 175 sets of plans were sold between 1970 and 1977.
About 175,000 sets were sold, at a price of £12 3s 4d each.
The last set sold at public auction went for $8 million.
By 1990, over 320 sets had been sold to 21 countries, many of which remain in service.
Two hundred sets of plans had been sold by 1979.
In 1903, 1,500 sets were sold, although no profit was made.
After retirement, 4 sets were sold for further use in Iran.
