This property in Laughlin went through several name changes.
I looked up the names/dates in Herz' Nevada Chips book to compare with TCR -- here's what it shows:

Herz
Sam's Town Gold River 1984-87
Gold River Gambling Hall & Resort 1987-92
Gold River [only] -- not listed in Herz
River Palms -- not listed. Opened after 1995 publication date.

TCR-15
Gold River, Sam's Town 1984-91 (It appears that TCR uses 1 listing for STGR and GRGH&R, in Herz)
Gold River [only] 1991-98
River Palms 1998-present

Based on the dates above, it seems that you could date your STGR chip to the 1984-87 period, per Herz listing.