Looks to be in reasonable condition. The chassis would clean up nice with a fresh coat of paints. In my opinion the SB45 are a great mower and I have learned heaps about them in the last 12 months while re-building mine slowly.
The engine looks to be off a Finsbury water pump, but dont let that worry you.
I would cable tie that clutch cable away from the mower as a precaution.
What are your intentions, does it run at the moment. There is a good video on this site of hew to remove the reel and bedknife so you can send them off to be sharpened, but are they OK at the moment?
