Lilly had one like that. 2 straight sides with POISON embossed and the third side was an arc for the label. Their's was more like 3" though. I have not seen one smaller.
Hi Steve, Good to see that you're back out digging! You have a small-size KV-1 Lilly poison. A cool bottle, seen in numerous sizes with POISON on the left, right or on both sides like yours. The KV-1s in amber are fairly common in the small sizes. Value is about $5-10. Clear and large-size amber KV-1s are worth considerably more. There is even a big amber one with a cool error- a backwards "N" in POISON. Must have been a drunken mold-maker [].
Watch out for small poisons that look almost like these KV-1s, but instead of having the rounded back, they are a true diamond shape. Those are KD-1s, and are much scarcer. They start at $20-30, and can go much higher depending on the variant. ~Jim