Restoring an old classic Webb cylinder moer

[amatureleccy]

Hi everyone, any thoughts on this.  I have picked up an old Webb petrol cylinder mower.  When I picked it up it was rusty, decrepit and destined for the tip.  So rusty that there were no labels on it so I don't really have a model number I can rely on.  It has a Briggs on it but that is fixed and works fine.  Trouble I have now is that, because I don't have a model number, I cant be sure of the parts list.    The nearest model number I have is AB1474.  That model shows that the height is adjusted by a lever that raises or lowers the front roller.  The difference is that mine is adjusted by a screw handle  - which of course is missing. 

The second photo shows where the screw handle would go.

Anyone know which model it might be and how I can identify the screw handle part number. 
Thanks

[Mick]

The model number you mentioned was from late 1970's - mid 1980's.  There was also a 250 and 253 from mid 1960's, and also a 277 from the 1970's All had a Briggs & Stratton engine fitted.

Assuming the engine is original then maybe we can narrow it down age wise via the serial number stamped into the engine cowl. First two digits of the last set numbers is the year.

[amatureleccy]

I have measured the width of the bolt as best I can.  It is about 7.3mm wide.  Looking to see if that was a standard sized bolt which, if it is, should make it easier to find a nut.  Question I have is, would it be a BSF or an SAE type thread?  Both seem to be popular in those days in automotive and machine engineering.

Thanks