I had one instance where a seller claimed not to receive my MO. It was for a $10 sale so I wasn't out very much. For $10 I did not bother following up on the missing one.
I received a USPS money order for a sale one time, I took it to a PO to cash. The did not want to cash their own MO, which I thought was strange.
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1971 Paramount P-13 Chrome
1973 Paramount P-15 Opaque Blue
1974 Raleigh Professional Blue Mink
1991 Waterford Paramount
Holland Titanium Dura Ace Group
Holland Titanium Ultegra Triple Group