The good news is you've got some reasonable pics and the reference number.
I don't know much about these 70's models but it looks like it could be ok.
Use the reference number to search for other examples and compare the font of the text, finish of the case etc to see if it looks correct.
I would say that looking at the dirt in the finer areas, it suggests to me that this has been given a quick spit and polish before sale, rather than a thorough clean and service. Also, these aren't highly collectible at the minute so shouldn't be too expensive.
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