Plural of grubstake; multiple investments of supplies or money given to prospectors or entrepreneurs.
Regular plural formation of 'grubstake' adding -s, or third-person singular present tense of the verb 'grubstake' (he/she grubstakes).
The fact that grubstakes are countable shows how real and concrete this practice was—it's not abstract investment theory, but actual bags of flour, pickaxes, and gold pans handed over for a shot at fortune!
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