Thunderbird TY-90 S/N 9053 bought new by Shade Tree Logging
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Turns out these 2 are the same machine Willapa Logging has it today (Cowlitz Log before them and Jerry Sorenson before them),there apre some recent pictures of it here: http://www.mylittlesalesman.com/ForSale/Details/1009974/0_Thunderbird-TY90-Yarder
Murk,would this be your seat at this time?