RARE Men's JAPAN Vintage 1975 Watch SEIKO "4004" 0903-7009. Navy Dial for Parts

I bought it from Japan as a untested one and I tried to replace the battery. 
The case back was also loose so I use some glue to put it back on. There might be glue residue inside the watch. Scratches on the crystal. 

The watch is currently running (surprisingly), but I do not have the confidence in guranttee itis functionality. 

So please consider it as a "runs with issues" watch and could need services soon. 

Serious buyers only, no return, thank you!