The Seiko caliber NE15B is a movement produced by Seiko Watch Corp. in their Seiko Instruments branch. This movement was released circa . It is an automatic movement with a ball bearing rotor.
Caliber NE15 VS NE15B:
The B at the end of NE15B indicates an evolution of the NE15 (NE15A). The official tech sheets for the caliber NE15B were updated on September 16, 2014. According to this post, the major upgrades included:
Add one jewel on main plate, barrel hole
Modify ratchet sliding spring
Modify date indicator maintenance plate
New balance wheel
Caliber 6R15C VS SII NE15B:
The caliber 6R15C is basically a Seiko-only version of the NE15B. Seiko Instruments (aka SII) sells the NE15B to other manufacturers (such as microbrands) for use in non-Seiko watches. Note: apparently some early versions of the 6R15C only have 23 jewels compared to the newer ones with 24J (the NE15B has 24).
Seiko claims that the accuracy of caliber NE15B is between -15/+25 seconds per day. This rating is based on normal daily wear on the wrist in normal operating temperatures. When testing your watch for timekeeping, make sure it is fully wound.
The caliber NE15B holds a power reserve of greater than 50 hours. To fully wind the mainspring, turn the crown a minimum of 55 times.
Crown Position Functions:
0 (against the case): Clockwise = Manual Winding / Counterclockwise = Nothing
1 (pulled out one click): Clockwise = Nothing / Counterclockwise = Date setting
2 (pulled out two clicks): Time setting clockwise and counterclockwise
To remove the stem, make sure the crown is in position 0 or normal position (not date or time setting position). There is a lever with a small indentation for your tool. Gently press down while pulling the stem out. See official instructions below for more guidance: