I put coffee beans(coarse grind) in a glass bottle and filled it with water(1 part beans to 5 parts water). I sealed this bottle and stored it in a dark cold place for 70 days. I opened the bottle today and filtered the coffee to another container. I don't see any moulds on the liquid or the container. I see a film over the liquid and I suspect it may be coffee oils. Is it safe to consume this coffee?
You left water and an organic substance (coffee) at an undefined temperature (but apparently not frozen) for a long time. There was no step to eliminate any bacterial or fungal load before sealing the bottle or at the time of bottling and no chemical preserving agent that may have done that in lieu of heating or prevented their growth during storage.
Technically, no, it’s not safe.
And that’s about all we can reliably say - „safe“ means that by all standards including some margin for errors it’s near impossible (or reasonably unlikely) that a consumer will experience a case of food poisoning when consuming the item in question.
What nobody can say without sending a sample to a lab it whether a non-safe item (without obvious signs of spoilage) actually does or does not contain harmful bacteria, fungi or their products.
What you do with your cold brew is up to you. I personally would likely discard it, both due to food safety considerations and because I suspect that the flavor after such a long time isn’t that pleasant, I guess the coffee is way over extracted, bitter and astringent.