That is an entry level bike in that brand. The component group was the least expensive group that Shimano made that year. The frame is hi-tensile steel with a cro-moly down tube (the big diagonal tube that says NISHIKI on it). Looks like the bike is in great shape and would be good for neighborhood cruises and gravel roads. If it fits and that is the type of riding you plan to do, hang onto it and enjoy, but don't sink a bunch of money into it.
Based on the component group, it looks to be around 1990 model give or take a couple of years. Value from a collector standpoint is negligible. You may be able to find a date code somewhere on one of the derailleurs to determine the age of the components and come pretty close to the year of manufacture. Enjoy!

 

Thank you for the info and advise. Really appreciate it. Yes, I'm leaning towards keeping it and just ride and enjoy it as is. I'm actually using it more than my better spec'd bike. There's just something magical with these older bikes. Cheers!