Thanks for this - Yes - I see now as I have an F1 and my K0 (both scraped around the 'Made in Japan ' lettering) - but I reckon you would have to be pretty eagle eyed to spot it on the bike.
I also notice that the casting above the 9 o'clock screw position hole is slightly different but could be machined away to look the same as the K0. Same around 1 o'clock hole position The main give away is probably the outside area around the HONDA lettering which is slightly larger on the F1. Think I will use it anyway and keep the original just in case I ever sell the bike - even the slightest bit of scraping around the bottom is so obvious on a restored bike and lets it down badly.
Anyone know what type is still sold by Honda (e.g from david Silvers, CMSNL etc.) I reckon it is probably likely to be a K6 style