It's not a crime to cash a check that someone voluntarily sent to you and that you believed to be in settlement of a disputed debt. For there to be criminal liability, there has to be criminal intent, and there is no evidence of that here. Even if they tried to press criminal charges, the police would not pursue it.
As far as civil liability
goes, if you had a dispute with the company, they sent you checks, and you agreed to accept the checks in order to let the whole thing go, that's called and "accord and satisfaction." That means that they agreed to resolve your dispute by sending you those checks (as did you). You would only be subject to civil liability if there were some paperwork showing that (1) they only intended to send you $X, not $Y and (2) you knew that you weren't entitled to the full amount when you cashed the checks. The judge would look at everything that happened, including whether the two checks were the same amount and whether a reasonable person should have known that they send one check as a replacement for the other (the lack of documentation saying that and the fact that they didn't place a stop payment on the first check would suggest otherwise).
Also, if you did not reach an agreement and they simply mailed you the checks of their own volition, and they sue for reimbursement, you would have the ability to countersue for the $250 you're still out for their breach of contract
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