Very interesting.
What you are saying is that the Marblehead 413 has a sequential production number of #182. This sounds like a very interesting piece.
As far as I know there are no # 413 Marbleheads (Stamp Series) with a number without the prefix.
But there was a big mix up at the factory over the numbering of the Stamp Series for the first 331.

The story goes like this.
The Cape Hatteras (open edition) came out in 1994 with a prefix of “A”. So when the stamp series came out in 1995 the manufacturer assumed that the next prefix would be “B” They produced 331 With the “B” prefix until Harbour Lights stop them and told them that each new Glow would start out its first year with the “A” prefix. The manufacture finished out the year with the “A” prefix.
For the year of 1996 Harbour lights had the Manufacturer produce the first 331 with an “A” prefix to fill in the missing numbers from the year before. Little did Harbour Lights know that the factory had all ready implemented a fix in 95 and had all ready produced the 331 with the “A” prefix. Most likely there are duplicate numbers of the first 331.
What you probably have is one of the factory fixes that had no prefix put on it. The factory might have realized that there was some kind of mix up and numbered some of them with out a prefix until they knew which way to go.
This is the first one I have heard of. Maybe St John or some of the other collectors have heard of a Marblehead glow without a prefix.

What is the number on the flag of the 30 mile point?

One more scenario could be that when the manufacturer switched over the numbering for the 30 mile point, St Joseph and the Spectacle Reef to the limited edition the numbering started all over again with the number 1. Maybe the factory started numbering a few of the Marblehead & Split rock just like the newly made L.E.