Here is a quote from my Spydiewiki files on the Mule Team series. I hope this helps.
Recalled due to improper heat treat. Subsequent heat treat fixed problem. Of the initial run of 600, only -450 were resold after the recall.
Re-treated Mules can be recognized by the underlined word Cruwear. This is the first Mule Team made out of a tool steel. Made on Golden, CO."