I can't speak on that specific coin, but the 1 Marks tend to go for way less than their cat price in the lower grades. I have bought many 1 Mark coins in AU grades for $1-2 each when their book price at XF is often in the 10-50 dollar range. With that being said, it is uncommon for me to see UNC or better coins of that type, and that's why their prices can be pretty high. That date is one of the lowest mintage dates, so it stands the best chance of bringing a high premium.
The more common dates with lower cat prices in MS63 are more likely to get close to their cat values, and this is consistent with most german series. I have seen people buying slabbed MS grade 1 Marks on
ebay in the 30-60 range with some amount of regularity and it's usually in the 25-50% below catalog range that's common. On most German series, the catalog price differences are less steep than the catalog would suggest. I would be surprised if you could find a buyer for that coin that was willing to spend over 1000 bucks on it, but they are hard enough to find where it's conceivable that sort of thing could happen. I see that that coin recently sold for 323 dollars on
ebay. That's sort of in the range I would have guessed. I wouldn't have been surprised if I saw a number in the 500-600 range, but 323 is in the ballpark of a realistic number.
I have seen older, nicer, and rarer German coins sell for 300-600 bucks, so I'd be surprised if someone would pay more for a fairly unglamorous coin type such as the modern CuNi 1 Mark.