1790? Portuguese ~36mm, 12.1gm Unknown Metal Coin, 20 Unknown Unit

I have tried all 4 of the '20' denominations under Portugal at PCG World Coin...an' drawn blanks. The date is worn enough that the last digit may be a 6 rather than 0; I cannot say for sure. It is very uniformly tarnished (toned?), enough that I can't say it isn't copper, or that it is silver. The 0 in 20 is far more worn than other areas on the (obverse?). I'm lost, obviously. Any assistance will be most helpful, an' gratefully received...Thanks for lookin'!

 

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Azores 20 reis https://en.numista.com/catalogue/pieces32652.html

 

Portugal had so many colonies and possessions back in the day! Many of the coins can be obtained inexpensively.

 

On the numista page it shows that these were overstruck on another coin does anyone know what they were?

 

Appears that a Portuguese 10 reis was used.
https://www.cointalk.com/threads/1795-azores-10-reis.9157/
https://www.ebay.com/itm/283837528204
https://www.worthpoint.com/worthopedia/azores-20-reis-1795-vf-overstruck-947064185

 

All very interesting! Mine shows none of the evidence of overstrike that these other examples have...but the zero in the 20 is oddly 'smeared' an' I haven't figured out what caused that...I suspect a fouled or damaged die, but I'm not at all versed in those kind of things.
Thank you, Each an' All...most sincerely for your illumination!
EDIT: This lone example on eBay shows very similar smearing of that zero! The seller also has Silver as the material, but it's copper of course.
https://www.ebay.com/itm/2567370474...PN9BBK9y5fhQmAPoH7ON3qYNk=|tkp:Bk9SR4Szy5v2ZA

 

I have a 1795 version of this. Definitely copper.

 

Here's my Azores overstrike. 1795 20 Réis
I think they used a Portugal 10 Réis as the base coin.
You can see quite a few details from the base coin under the "20"

 

You can see a lot of the under type on that one!

 

It is one of my favorite coins because of that. I don't have my notes with me but I was able to identify the under type.