How would you explain “1000 years old “ in this sentence?
The scientist wants to revisit the location where five coins were found in the Northern Territory in 1944 that have proven to be 1000 years old, opening up the possibility that seafarers from distant countries might have landed in Australia much earlier than what is currently believed.

How would you explain “1000 years old “ in this sentence? Does it mean the coins have proven to be 1000 years old?
Thanks!

Question

How would you explain “1000 years old “ in this sentence?
The scientist wants to revisit the location where five coins were found in the Northern Territory in 1944 that have proven to be 1000 years old, opening up the possibility that seafarers from distant countries might have landed in Australia much earlier than what is currently believed.

How would you explain “1000 years old “ in this sentence? Does it mean the coins have proven to be 1000 years old?
Thanks!

Answer

Yes, it is saying that the coins have been proven to be 1000 years old.

For this example, only "I" and "you" does not follow this. For "I" and "you" use "have been." The other subject pronouns follow this rule:

Has been = singular
Have been = plural

"the Northern Territory" can be thought of as "it"
It has been...

"five coins" can be thought of as "they"
They have been...

I hope this helps