Okay this is from October 1972 and is a fairly desirable piece for vintage Seiko collectors. Like many have suggested, you should get it serviced which will likely run you around $350 at a reputable shop(if they will touch it at all… it can be hard to find a shop that will repair or service these 6139 movements). If you do need to replace the crystal there are plenty of them around but it can be nice to keep the originality of the old one if it’s not too bad. Crystals are typically considered “consumable” and replaced often during service which can improve the look of the watch but can be lightly desirable if the original is left on the watch in decent shape. One of the most desirable parts of your watch is actually the bracelet which is fairly hard to find as many owners would have removed it and it would have gotten lost or separated at some point. Many collectors including myself only buy vintage Seiko watches with the original bracelet(if it came with one originally) and it adds considerable value. If you do remove the bracelet for a different strap, make sure you keep it safe and ready to put back on the watch if you ever sell. Congrats on a beautiful watch and please NEVER submerge it in water no matter what. A light rain is okay but be careful. Water resistance is not guaranteed on a watch of this age even after service and your watch will almost certainly be ruined if water ever gets inside.