Help identifying Norwegian marks from 18th century spoon

[ilovespooning]

Hello. I've been able to identify this spoon as being from Norway, but would very much appreciate help in learning more about the marks. The spoon weighs 55.5 grams and has been engraved twice: the first .G.A.S. the second ENJ 1810. It has a hand engraved or etched shell pattern.

The town mark is a crowned G (with small VD underneath) - unknown
The assay master's mark is a P over 91 or 97 - could be Peter Petersen? unsure what 91 or 97 is, the year?
The maker's mark is IS over 8Z - could be Jacob Steen? unsure what 8Z or 82 is?
The last mark, date mark(?) - maybe Pisces 1766-1820?

This is just what I've been able to gather from internet searches, but I'd like to learn more and to clarify if I've got things right. There is so little information on the internet (that I can find) about silver from this time and this is my first old Norwegian spoon. Thanks very much for any help!

[AG2012]

Hi,
The marks explained:
[1] C / VD below a crown, all within an oval reserve (Christiania town mark)
[2] P /97 within an oval reserve (cameo) (combined warden's mark and date mark for 1797 used by Peter Petersen, 1782–99);
[3] IS / 82 within an oval reserve (cameo) (maker's mark of Jacob Steen, born about 1740 in Bergen, working in Christiania in 1782, alderman (oldermann) in 1785, died 1804);
[4] Zodiac sign for Pisces within an oval reserve (cameo)  February 18 – March 20

Regards

[AG2012]

Complete set of Christiania marks from the 1780s, city mark, guild mark for Peter Petersen 1789, master Jacob Steen 1782, Scorpio (October 24 - November 22). Store Norwegian lexicon.

[Qrt.S]

A bit more info:
Jacob Steen is the son of master Hans Bierregaard (1746-1778) in Bergen. He was journeyman with master Christopher Linde (1753-1764) in Bergen to 1760. Jacob Steen became master in Christiania (Oslo) 6.6.1765. Alderman 1785-1791 and he passed away 19.11.1804.

[ilovespooning]

Wow, thanks everyone! I really appreciate your assistance in me learning more about this spoon :)

What was the silver standard at this time?

Is this a rare piece?

Did you use a book/text as a reference?

Thanks!

[Qrt.S]

Since 1608 the fineness was 13½ loth (843/1000) to around 1820-30. From that on is was lowered to 13¼ (~830/1000). As from 1892 punched 830S
The sources are books: "Norsk Sølv gjennom 600 år" and "Norske Gull- og Sølvstempler"

[ilovespooning]

Thank you again! I really appreciate being able to add this information to my silver hallmark identification skill set.