in the period 1922-1927 well over half the fleet of d engines were renumbered, some twice, to clean up the mess left behind by the former odds/evens system and group engines of the same design into a consecutive series. in 1922 the proposed range was 490-799 for the d engines and 250-269 for the formula_1s, although in practice the ranges ended up as 500-799 and 250-287 with many numbers unfilled. note the total of these groups would have been 350 engines, against 319 actually built. during this period two of the formula_1 engines were converted to tender engines, one sold and a further 17 scrapped.