LEWMAR, WHITLOCK  Mamba BH10 Steering Head 
Part No. 89201067
Serial No. 07/04/06-2341
There is another label 026740
Overall size 250 x 190 x 90 mm
Standard taper for wheel with key and without nut
Missing 2 x M8 socket head screws
1:1  1 rotation of wheel gives 1 rotation of output shaft

Taken from Lewmar catalogue. Mamba is a Lewmar trademark
The Mamba System provides the ultimate in marine steering in terms of precision, feedback and strength
Chosen for a diverse range of sail & power craft such as bluewater cruising yachts, pilot vessels and sail training vessels
Mamba is a Lewmar trademark

List price is in the region of £1150

 I have many years experience of selling Lewmar products and have extensive knowledge for providing spares for winches, windlasses, steering and deck hardware