Tarnishing of Seiko SGP gold plating during storage

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Seiko7A38
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Tarnishing of Seiko SGP gold plating during storage

Post by Seiko7A38 »

I'm not sure what process Seiko actually used to apply their 'SGP' gold plating to two-tone and gold tone watches. I've tried googling without success. However, it appears to have a limited life span. It's not uncommon to see watches like the gold-tone 7A38-7000 with varying degrees of tarnishing (or even rust) creeping from underneath the gold plating. Another problem area that frequently succumbs are pusher cups; particularly on the gold-tone 7A38-7060 and Italian market 7A38-706A variant. Presumably it's caused by a delayed chemical reaction with the differential base metal.

Although some people have successfully managed to temporarily remove it, by polishing, it usually re-appears later. Personally I always try to avoid buying watches that are showing any signs of it. As I've mentioned a couple of times recently in the WRUW thread, I've been gradually re-organizing my various collection boxes, over a period of months, taking stock. In doing so, I've re-acquainted myself with a few unloved watches that I've owned for a good many years.

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Re: Tarnishing of Seiko SGP gold plating during storage

Post by Seiko7A38 »

One such 'unloved' watch is my sole example of the two-tone 7A38-727A SAA132J, which based on the fact they only ever seem to turn up on eBay Germany, I've always assumed to be a German market model. I bought it in June 2009, winning a German eBay auction for 53.60 Euros. Here are the two small eBay listing photos:

7A38-727A-Stainless+Gold-SilverFace-eBay(Germany)-June2009-1.jpg
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It's far from mint, in what I'd class as only average worn condition, but a decent enough example to have remained in my collection, without my feeling the need to actively seek out another in better condition. The strange thing is that over the last 10 years or so, I don't ever appear to have taken a wrist shot of it. This side-by-side comparison shot (with my two-tone 7A38-7190) is all I could find.

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Re: Tarnishing of Seiko SGP gold plating during storage

Post by Seiko7A38 »

As you can see from that photo, taken back in May 2010, although there's some scuffing and slight loss from the rim, the bezel's gold plating is bright and shiny. So you can probably imagine my horror, when I took it out of my collection box, to replace its battery yesterday morning, to find how badly it had deteriorated.

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The tarnishing extends all the way round the bezel, although this artificially-lit shot of the 12 o'clock side doesn't show it particularly well, it's nearly as bad. :(

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Re: Tarnishing of Seiko SGP gold plating during storage

Post by Seiko7A38 »

I've no idea what caused this sudden deterioration. No other watches in that collection box, where it's lain neglected for probably 10 years, have been similarly affected. There are still a couple of small packets of desiccant silica gel in the bottom of the case, which are bone dry. The old flat battery I removed (a Renata #394) showed zero signs of leakage. Nor, best I can recall, have I ever attempted to polish the bezel's gold plating, at any time during my ownership.

I'd remembered seeing something similar fairly recently on another two-tone 7A38-727A, which if my memory serves me correctly, was listed by profiteering German eBay seller m.a.k.2979 earlier this year. A quick search of my photo folders yielded these few from his eBay listing in February of this year. The watch wasn't in such good overall condition as mine and the fourth image shows comparably worse plating deterioration.

7A38-727A-Stainless+Gold-GreyFace-eBay(Germany)-Feb2021-(Re-seller)-1.jpg
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Re: Tarnishing of Seiko SGP gold plating during storage

Post by Seiko7A38 »

Well I haven't found an answer to whatever may have caused that tarnishing, but I do have a solution in hand, in the form of a replacement NOS Seiko p/n 82341021 bezel. There were other possibly more deserving candidates I could have fitted it to, but my two-tone 7A38-727A had become the most needy. Note the matt gold finish of the bevel.

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Oddly, when I levered the old bezel off, there was absolutely no sign of tarnishing on the underside, nor any rust on the case mating flange, where I'd half expected it might have emanated from.

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I fitted the NOS bezel this lunchtime, re-using the same replacement Sternkreuz p/n MSM310 crystal I'd fitted 10 years ago, the original clear crystal gasket and white nylon bezel to case gasket. Both were still an exceedingly tight fit.

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