Spanish 8 Reales?

I came across this coin very randomly and bought it on impulse. I'm pretty new to coins but I felt like this one was rare. I've been looking around and it seems to be from 1600s Philip III. Can anyone confirm this or let me know if it's real/valuable?

If it is not replica it indeed fairly valuable. Last one in decent state I saw in the store was offered for  350$.  However chinese counterfeiters in last two decades made a huge ammount of replicas of many silver coins from 1600-1800 period, and this coin in particular was replicated in large. So before you can be sure that it is valuable item, you should consult with specialist and ensure its genuine. Cheers

What is the size and weight of the coin, please.

Welcome to Numista. Correct orientation. Yes, based on the shield, it is representing itself to be that of Phillip III (1598-1621). These are notoriously difficult to date, identify, and authenticate. More information on your example please.

tdziemia

What is the size and weight of the coin, please.

It weighs 5g and is almost exactly 1" across 

So, not 8 reales, maybe 2 reales (and light for that denomination).

I'm not sure what the original size or weight would be, however there are a few deep scars and one side looks to have been clipped or broken off at some point. I'm sure that was a significant amount of (relative) weight but that seems common for older coins like this one

I thought the blue circle to the right of the shield might be II, as in 2 reales. I don't like the Lions highlighted in blue around the cross as they appear to be more like stick figures rather than lions. Mushy through the nature of it's crude manufacture and wear is one thing but these stick figures raise a red flag to me and just don't look right. The embellishments around the Greek cross are mushy and suspect as well. I'm inclined to think this is trying to represent a Spanish colonial and not a coin manufactured in Spain proper. As you said, the weight discrepancy could easily be explained by clipping as was rather common so that would be the least of my concern with this example. The proper weight of a 2 reales coin should be around 6.8 grams. The diameter for a 2 reales coin should be roughly 28mm or slightly over an inch. Clipping would compromise diameter as well. I am undecided on authenticity.