Most visitors online was 1660 , on 12 Dec 2020
Congratulations, a spectacular Rockford.Since the case is stamped with "SKS", which stands for "Seikosha", I believe that this Longines imported only the movement and cased it in Japan.
I feel that I see pocket watches with blue jewels more often in Japan than on ebay, for example.
ロンジン 懐中時計 ブルーサファイア ダイヤモンド受石
ユリス・ナルダン 懐中 ブルーサファイア
INTERNATIONAL WATCH CO. 懐中時計 - スイス製
本日の１個！（ミドー青石懐中、パワーウォッチの補足） - 古時計と小物の雑貨屋 モキ＋（モキタス） 富岡八幡宮骨董市に出店中！！
This leads me to speculate that the demand for blue jewels was very high in the Japanese market at that time.