What qualifies as a "PMM" is up to your client.  There is no legal significance to a Purchase Money Mortgage as far as I know.  I don't think you will find any mention of a "PMM" in the Ohio Revised Code, nor the Marketable Title Act.  It is simply some point in time that the client, or their underwriter, is willing to take the risk on any title issues existing previously. 

The theory is that if you have a "PMM" the transaction was most likely insured and any problems would have been discovered and corrected.  I do not think that is a safe assumption, but many seem to rely on it. 

Best,
Robert A. Franco
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