This example has been heavily rebuilt, sadly. In a decrepid ex-quarry state, it would be much more interesting and have loads of character.
To check if it was originally Penrhyn, count the spokes on the wheels. If 7, almost certainly Penrhyn.
They were known as runner wagons or tenders. In the quarry, most locomotives had one behind them to carry essentials like coupling chains and oil cans.
If I knew how to attach a photo I'd be able to show you how they looked when in the quarry, all battered and worn.
Penrhynman