Nikon Nikkor 18mm f4

At the time of its introduction one of the widest lenses which can accept front filters. Introduced as a K (New Nikkor) model, it was upgraded to Ai with only minor changes.

Version Serial no Date Screws Engraving Notes
K,Ai 173111 < 173275 – 177425 > 177387 Nov74 - 1977 5+ LMIJ Name engraved on ring inside filter. Many Ai lenses in this range made using old parts.
Ai 190001 < 190138 – 190657 > 1977 - 5+ LMIJ New serial number block for Ai version. Early lenses with name inside filter (like K type). Thick rear lens protector.
Ai < 190902 – 191165 > - 3+ LMIJ Name outside filter ring, thin rear lens protector.
Ai < 191245 – 193859 > - Mar82 3+ MIJ -

Version	Serial no	Date	Screws	Engraving	Notes
K,Ai	173111 < 173275 – 177425 > 177387	Nov74 - 1977	5+	LMIJ	Name engraved on ring inside filter. Many Ai lenses in this range made using old parts.
Ai	190001 < 190138 – 190657 >	1977 -	5+	LMIJ	New serial number block for Ai version. Early lenses with name inside filter (like K type). Thick rear lens protector.
Ai	< 190902 – 191165 >	-	3+	LMIJ	Name outside filter ring, thin rear lens protector.
Ai	< 191245 – 193859 >	- Mar82	3+	MIJ	-

Links

Collection of Richard de Stoutz

Article at Photography in Malaysia site