There’s something special about finding a watch in a mixed lot that immediately stands out. In this case, it was a Seiko 7005-8190 with a unique purple-patterned dial—subtle in some light, vibrant in others. It wasn’t perfect, but it had character. And more importantly, it had potential.

First Impressions

At a glance, the watch was in decent shape:

• Watch is running which is a good sign
• Scratched crystal, light case wear consistent with age
• Dirty movement and likely haven’t been serviced for several years

Despite the cosmetic flaws, the dial was the star of the show. The purple design gave it a distinct personality that made it worth the effort.

Diagnosis

Putting the watch on the timegrapher showed something unexpected:

• Unusually high amplitude which spikes to 330, there is no manual wind on this movement and this was just a few seconds of auto winding so this is not normal. There is potential for over banking which could damage some of the watch components like the escapement.
• High beat error indicated the balance wasn’t centered properly
• Running fast

Since it was running, I’ll start with a proper servicing.

Dating the Watch

The Seiko 7005-8190 sits firmly in the mid-1970s, and this particular piece can be dated more precisely using its caseback serial number. The 7005 movement itself was widely used throughout the decade, but this reference—with its textured, slightly experimental dial—fits right into that era where Seiko was pushing more distinctive designs. The purple-patterned dial is a great example of that, subtle at first but full of character once revealed.

How to Date Your Seiko (Caseback Method)

• The first digit represents the year (within the decade)
• The second digit represents the month
  • 1–9 = January to September
  • 0 = October
  • N = November
  • D = December

Based on the caseback serial 411493, we can decode the production date using Seiko’s standard format:

• The first digit (4) represents the year (1974)
• The second digit (1) represents the month (January)

This places my watch at January 1974, right in the heart of the 7005’s production period.

It’s a nice bit of context for this restoration. What looked like just another average watch from a quiet lot turned out to be a clearly dated mid-70s Seiko—made even better by the fact that its most interesting feature, the purple dial, was hiding in plain sight under a worn crystal.

The Disassembly

This is my first Seiko and first Japanese automatic that I disassembled. The movement inside is 7005A as written on the bridge. The 7005A movement is seems straightforward, and there is actually a Seiko guide available which I learned after, in hindsight it could have made the disassembly easier, but still good learning by winging it.

Step by step teardown revealed:

• Old, sticky oils across the gear train
• Dirt buildup in key pivot points
• A worn mainspring that had likely lost its elasticity

Nothing unusual for a watch of this age, but enough to explain the poor performance.

Cleaning and Inspection

All components went through a ultrasonic cleaning cycle (distilled water and mix of cloudy ammonia), then dipped in lighter fluid to remove the access water, after drying, each part was inspected carefully:

• Wheels checked for damage or bent pivots
• Jewels inspected for cracks or debris
• Escapement components examined under magnification

Thankfully, everything was intact—no major parts needed replacement beyond the mainspring.

Reassembly and Lubrication Attempts

Reassembly is where the real investigation happens. Proper lubrication is critical, especially for improving amplitude.

Key points during this stage:

• Barrel walll oiled with the proper grease for automatic – I had to order another Moebius Grease 8217.
• Fresh mainspring installed to restore power delivery
• Correct oils applied sparingly to pivots and escapement – ordered a new oil Moebius 9415 to oil the pallet stones that gets transferred to the escapement teeth
• Balance reinstalled and adjusted to reduce beat error

Everything looks good on assembly so far.

Results on the Timegrapher

This was the first attempt.

• Amplitude was still low 170-180
• Beat error brought down to acceptable levels
• Rate was not stable.

It needed a more close inspection on what was going”

• The hairspring seems to be sticking, indicating it could have been magnetized or not cleaned properly.
  • I demagnetized it and it improved the amplitude and rate, I observed the behavior for couple of hours, releasing the power and jump starting the balance wheel. The hairspring would start sticking again, so there is likely problem in the cleaning process.
• I disassembled the movement and clean it on a new DYI cleaning process. – I left out the mainspring as I thought was alright as it’s a new mainspring.
  • I have two jars of lighter fluid, with 3rd jar being optional
  • I hook the basket to a drill and dip it in the first jar and let is spin for 3 mins, then rinse it for 3 mins on the next jar.
• I assembled everything back but the amplitude was still low, though the rate has improved.
• Then another disassembly and this time closely inspecting the barrel, pre- cleaned it, ran the whole parts again on my DYI cleaning process.
• This time I put a thin strip of grease to the mainspring by running a piece of watch paper with the Moebius 8217.
• Next, I oiled the barrel wall again and this time added some to the floor as well.
• Then, finally put everything back together.
• Amazingly the amplitude picked up at 250-270 after the assembly. I was so happy with that.
• I fixed the beat error and lowered the rate as it was running fast.

It’s always satisfying seeing a movement come back to life after service—especially when the improvement is this noticeable.

Case and Crystal Work

With the movement sorted, attention turned to aesthetics:

• The crystal was polished to reduce visible scratches (or replaced, depending on condition)
• Case lightly cleaned while preserving original finish and character

I prefer not to over-polish vintage cases—keeping some wear maintains authenticity.

Final Thoughts

This restoration is a great example of why watch lots can be so rewarding. What started as a “working but tired” piece turned into a reliable, visually striking watch. And I learned a lot during the process.

The purple dial gives it a unique edge, and now with a healthy movement inside, it’s ready for many more years of use.

And I learned that vintage Seiko movements doesn’t have any manual wind which was something tricky to regulate as what is a normal reading. But it was a good learning experience getting familiar with Japanese movements.

Would I flip it or keep it? That’s always the tough question. Pieces like this tend to stick around a little longer.

If you’re working on similar vintage Seikos, the takeaway is simple: even if a watch is running, don’t assume it’s healthy. Low amplitude and high beat error are often signs that a proper service will completely transform the watch.

And sometimes, hidden in a random lot, you’ll find something genuinely special.