Interesting reflections here regarding Investor’s valuation and an appropriate premium. Based on the company’s history, one could even argue that a NAV discount isn’t justified in terms of returns, as Investor’s holdings have performed so well. Of course, there are many other reasons why the market applies these to investment companies.
Regarding Investor’s current valuation, I would say that the excellent share price performance is partly a risk, as it has been driven specifically by Saab (P/E ~50), Atlas Copco, and ABB, which are valued with very optimistic P/E multiples of ~30. These are certainly high-quality companies benefiting from strong trends, but since these (very) highly valued companies make up 35-40% of the NAV, their valuation multiples had better hold; otherwise, the NAV and share price will come crashing down from that ATH.