Plenty of grading scales out there , all of which regard a cracked record as near worthless from a collectors POV ... 0-5% of Mint value.
But there are plenty of desperate wannabees out there that seem to disagree and pay way over the odds for f*cked forty-fives on an hourly basis , especially on the bay.
This will no doubt kick off yet another heated debate where a lot of folk will state that "Norvern Soul' is a "special genre" that doesn't need to use a proper grading scale as the tunes are so sought after that you can name your price regardless of condition.
Personally I prefer to use the 0-5% rule as it's the generally accepted valuation across the globe regardless of genre or medium but that's just one opinion.
I guess that a M- record that's cracked but plays through with a minimum of 'clicks' would be the origin of the so-called "OK for DJing" grade that has become so common in listings , still only 5% of mint in my book though , and that applies to any 45 whether it be a £25 tune or a £5000 one.
Touch paper's fizzing , fire away ......