Hard to estimate value without seeing. I had an Otto Geyger in 8x60RS built in 1929 I believe. Definitely a Best grade double. The 8's can be J or S bores look on the water table and it will tell usually if not you have to slug bores. Handloads are no problem as you have .318 bullets readily available. Value of mine was in the $4000/5000 range. It was a nicely engraved Greener crossbolt action with most of original case good. Bores were perfect and it shot well. Geygers are very well built guns, at least the ones I have seen or read about. Manufacture date will also be on water table (action flats).