Forks 18 cm are also called diner (small) forks.
The forks, maker's mark only, monogram HL(
without serif's) conjoined in rectangle.
Citroen, indeed mentions a HL for an unknown silversmith active in Leeuwarden 1711-1746 . However
https://www.zilverstudie.nl/ Jan Schipper mentions; HL (with serif's) conjoined in circular frame for Henricus Ludinga, Leeuwarden year-letter for 1714 and for 1724. Frisian guild silver below 1st standard 934/000, no town mark, no year letter and maker's mark only. Silver fineness around 875/000.
We also can find HL (
without Serif's) conjoined in a rectangle for Hermannus Langelo, registered in Zuidbroek in the province of Groningen, 1807-1826. It is not unusual to see Groningen silver with only a master mark. Certainly not in the time period 1795-1813, during the French occupation.
Peter.
Source;
Karel Citroen, Dutch Goldsmiths and silversmiths marks and names prior to 1812. Jan-Pierre van Rijen, Groninger keur Zilver uit Stad en Ommelanden. Jan Schipper Zilverstudie.