Given the description so far, no it's not one of the more desirable/more valuable models. Shimano Light Action was at the lower end of their product line. Somewhat smallish seat post OD (the better the model, the larger the post diameter). Shimano, Dia Compe, and others made a wide variety of components from really basic to really great and everything in between. This is why you will see bikes at Walmart advertised as "Shimano".


Serial number at best just indicates year bike was made.

Identifying features: tubing decal on frame describing tubing used to make the bike. Model of components. Date code of components. Seat post outside diameter (you got that). Is RD claw mount or attached directly to frame? Are seat post and handlebars steel or aluminum? Are chain rings steel or aluminum (magnet will tell you). Pedals are super easy to change, so in 30+ year old bike, they likely are not original.

Finally, your location can have a major impact on value. A bike could be worth $25 in one town, and could be worth $175 in another town.

True restoration is a guaranteed money losing proposition. Doing basic maintenance may give you a slight return. Doing basic maintenance and continuing to enjoy riding it will give you the maximum return!!

You can read several recent threads where many of us lament the downturn in value of vintage bikes. In my area, everything but the very best has dropped about 50%. The days of refurbishing a middle of the road vintage bike and making a decent return for your investment is over. I now save my time for really special bikes or for parts. The better parts can still be financially rewarding.