This is the Ronda caliber 515.24H (24H for 24 hours) which is basically a caliber 515 with an added GMT complication. It is a Swiss made or Swiss parts quartz movement. This caliber is also sometimes written as 515H.
“Affordable metal movements for reliable quality watches.” -Ronda
This caliber features:
Repairable metal watch movement
Power saving mechanism with pulled out stem: Reduction of consumption approximately 70%
Interchangeability: All versions 11½”’ with same movement height 3.00 mm and stem height 1.50 mm
Very powerful stepping motor
*Pulled out stem refers to pulling the stem in time setting mode, not removing the stem completely from the watch.
Swiss Made VS Swiss Parts:
There are several caliber 515 based quartz movements by Ronda. There are Swiss Made and Swiss Parts versions available. Both are nickel plated metal, both have 1 jewel. Ronda documentation claims an accuracy of -10/+20 seconds per month, regardless of the movement being Swiss Made or Swiss Parts.
Where is the caliber number?
Ronda does not stamp the metal part of this movement with the caliber number, instead, you can find a reference on the outer plastic part of the movement. It is not the full caliber number (515.24H) but the base caliber.
Ronda Stem Positions:
The better understand time-setting and disassembly instructions, it is important to understand how the manufacturer describes certain states or modes of the watch. According to Ronda, the crown/stem positions are as follows:
Position 1 (I) – Position of rest. Crown against the case with the watch running.
Position 2 (II) – Crown in date setting mode. In the case of the caliber 515.24H this is also the position for setting the GMT hand.
Position 3 (III) – Time setting mode. This position will also hack (stop) the seconds hand which also serves as a power saving mechanism.
To remove the crown/stem, find the hole with the arrow. While the crown is in position date setting mode (position 2), pressing this with your tweezers or other tool will allow the stem be unlocked so you can pull it out.
Changing the battery:
The correct battery cell for the 515.24H is number 371. Ronda claims that the battery should last up to 45 months. To remove the battery, there is a metal locking mechanism that uses tension to hold it into place. Gently put your tweezers or other tool in the hole and slide it over – not too hard and not too far. The battery will pop out like in this video. Do not remove the screw and do not touch the coil.
The thin orange/brown colored disc or tab below the battery is an insulator. It is necessary to prevent shorting out the battery. If your watch doesn’t work after installing a new battery, it’s possible that the insulator fell out, or the new battery cell could be bad.
As mentioned above the caliber 515.24H has a built-in power saving mechanism. If you are not going to wear your timepiece for an extended period of time, you can pull the crown out to time-setting position to reduce drain on the battery. Keep in mind that this also puts your stem and crown in a vulnerable position, so be careful about how you store your watch with the crown pulled out.
At the time of this post, replacement prices for the 515.24H were found online in the range of $11.95 – $19.95 USD. It is unclear whether these are Swiss Made or Swiss Parts.