But we are talking about Tickfords, not Welders.
	
	
		I quoted the general changes to get an idea of the month of production of the vehicles, rather than when the number changed in the Tickfords/Welders production series.
To set the record straight from TP 111/G 7th Edition
The Fishplate chassis ended with General Production 06103840; Tickford 06200091; Welder 06300021.
The headlights through the grille [Grille panel assembly (part #236109) and grille (#301900)] began with General Production 06111547; Tickford 06200312; Welder 06300031.
The 2 1/2" wide front springs were introduced at General Production 06113530;Tickford 06200410; Welder 06300031.
So, the Tickford vehicle in post #22 (06200379) is correct in having the headlights through the grille.
General Production 061xxxxx (15,440 produced in 1950); Tickford series 06200xxx (480 produced in 1950); Welder series 063000xx (30 produced in 1950). 
It would also appear that 70 Tickfords and 10 Welders had been built in 1949 and a further 100 Tickfords and 20 Welders were built in 1951. Tickford production then ceased but 36 Welders were built in 1952 and a further 22 were built in 1953 after which they did not have a special series of their own (From Mike Combridge's research).  
Bob