K11 Fordson Tractor variation

[MatchboxFreak]

Has anyone noticed the casting variation on the K11 Fordson Tractor hook?
Some (most?) trailer hooks are a circular arc segment (almost 3/4 of a circle). Some trailer hooks are squared off on the top rear quadrant.

I haven't figured out how to upload images directly from my phone to this site but Nick's page on the K11 shows the two variations.
http://www.vintagebritishdiecasts.co.uk/kings/k11-1.htm
Lot 555 shows the 3/4 arc segment trailer hook.
Lot 1034 shows the squared off trailer hook.

Since Lot 555 has the un-painted steering wheel it seems this is the earlier casting.
Lot 1034 has orange wheels.
My Fordson with the squared off hook has red wheels.

Are there other casting variations?

Thanks and happy hunting!
Kurt