It is a prince's crown, but the L is much more likely a surname.
Never with aristocrats you will find the surname, only the first name.
If that shotgun had belonged to a prince from a sovereign ruling house, my suspicion is that it would be considerably posher and more elaborately engraved, and it would bear a full armorial achievement (coat of arms), not simply a prince's crown.
And only princes from ruling houses get called "Prince Personal Name." The non-sovereign prince typically is called "Prince Surname."
There are heaps and piles of non-sovereign families is numerous continental European countries with princely titles. And many are by no means fabulously wealthy.
