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This model is the Corgi 409-B-1 Mercedes Benz 406 Unimog Dumper in dark blue and bright yellow.
The only operating part on this model is the rear dumper (operated by a side lever). The cab and rear lower bed are painted dark blue, with the front bumper and wheel arches painted bright yellow, The front headlights are jeweled lenses and the Mercedes front symbol appears to have been silver foiled. The rear dumper body is bright yellow, and the model has a separate dark grey chassis casting.
The interior is red plastic with a silver grey steering wheel and the vehicle cab is glazed with clear plastic.
All wheels are of a 4 spoke agricultural type - dark red metal wheel hubs, each with a separate heavy tread rubber tyre, mounted on steel axles.
The base plate is really the chassis casting in dark grey painted metal. It is marked in the middle centre with "CORGI, TOYS" on two lines, the left chassis rail carries "Made in Gt. Britain", and the right chassis rail has "Unimog, 406" on two lines. This chassis casting also carries two silver metal components representing the front and rear drive shafts and differentials. It is held in place by two machined rivets.
This casting was issued between August 1971 and 1972 and 135,000 were sold (pg 213, "The New Great Book of Corgi Toys 1956 - 2010" by Marcel R. Van Cleemput, published 2010 by New Cavendish Books [ISBN 978 109 4562 10 8]). The scale was stated at 1:48.