Smiths pocket watches - worth a punt?

[Geralt]

Have seen a lovely ATP style dial/handset Smiths pocket watch on ebay, looks to be from the 60s, I'd guess. Case looks to be in good fettle with only minor scratches and the hands/dial are clean and tidy but no pics of the movement, described as 'working'. Seller is not an expert and has 100% feedback.

ISTR these were made in Wales in their thousands, which is the extent of my knowledge. A quick Google hasn't been particularly enlightening as far as the movement goes.

Don't know whether I'd use it much, but the idea of owning a piece of British watchmaking history for not much money is appealling.

Would probably want a new crystal and mainspring at least. I'd prefer to have it properly serviced and keeping relatively good time if poss, rather than have it as a non-running paperweight. Are these worth the cost of a service or not really worth spending any money on?

Any thoughts/info would be appreciated.