Hello there!
You have a nice looking Kbk. Wz. 1898 (Polish K98), I would venture to guess that it may have been reblued at some point, as there are some lack of sharpness on some of the markings/serial number and the finish is glossy. I am assuming you have the rest of the components (triggerguard/floorplate, bolt, stacking hook, front and rear barrel bands, etc)?
Re-stocking these is a bit of a struggle, as there aren't too many "compatible" donor stock options. However, there are several options you can pursue for stocking this rifle, it all just depends on how "correct" you want to be:
1. You can get extremely lucky and find yourself a Polish K98 stock, however these are extremely hard to find these days and come in two "tiers". The higher tier is finding a Polish military marked K98 stock which will have a serial number on the bottom of the buttstock, Polish eagle proofs on the semi-pistol grip, and Polish stamps on the right side of the buttstock. You can expect to pay $600+ for these. I was lucky to purchase one from another collector (who found one for cheap languishing at a "spare Mauser stock" pile at his LGS).
2. The second tier of finding a Polish K98 stock is getting lucky and finding a scrubbed SCW export stock. These will have their original Polish markings sanded away and will have a new Spanish serial number stamped on the left side of the stock above the recoil lug, and some will have an MP8 flaming bomb proof on the right side of the buttstock. These are still rather hard to come by, but a bit more affordable. This is before my time, but when Springfield Sporters was still around, they had these stocks available for folks that were restoring Imperial German Kar98a carbines and Polish K98s. That well has run dry ages ago...If you are desperate and have the cash to spend, one thing you can do is find a cheap SCW Polish K98 on GunBroker or locally, and sacrifice it just for the stock (and any missing stock hardware). I personally would be willing to gut a scrubbed rifle if it means completing a crested example.
3. If you still want the rifle to be "Polish" but not necessarily correct, you can find a SCW export Wz.29 short rifle stock for this rifle. There will be a gap in the receiver cutout of the stock, since a Wz.29 is a large ring receiver and the K98 is a small ring, but the stock for a Wz.29 will readily accept a K98 otherwise. These seem to be the most "common" Polish stocks to find out in the wild, but they aren't as easy to find as a K98k stock. I know Apex Gun Parts had a small handful recently in fair condition recently on their website and eBay.
Good luck!
