Their loading data for 338 Lapua Magnum shows using N160, N165, N170 of the common powders and all are slower stick powders which is to be expected. There is also N560 in their 500 series and 24N41, I doubt it was any of the latter.
If there is the small white sticker on the bottom with the batch / lot number (sometimes that sticker shows a year) you can maybe contact them and find out exactly what it was.
Since you opened it breaking the seal it was a good sealed container. Heck, if they can ID it based on lot number I wouldn't hesitate to use it. Long as it was sealed and you can get a good reliable ID of it. The VihtaVuori powders are great stuff and they aren't cheap. Eight pounds of N160 runs about $190.
Something you can try is contacting Kaltron Pettibone 800-683-0464 as they are the importer. Powder Valley who sells the stuff only shows the VIHTAVUORI N160 as being sold in 8Lb containers and not the N165 or N170. I don't know but if you have a lot number it can't hurt to make a call.
Ron