NavList:

I have always understood that the Chinese versions were copies of the Celestaire design Ken Sr had made in China.  The source for this is Celestaire catalogs from years ago.

I have just come across some very helpful information in Bill Morris's book on The Nautical Sextant, which I hope I may quote here:

Much of the history has been lost with the passage of time and the fog of civil war. In about 1940 a factory began making sextants designated GLH 130-40. It may be that 40 refers to the year of first manufacture, but at any rate, it was a copy of the C. Plath wartime alloy instrument that later appeared in the USSR as the SNO-M, and was produced only for the Chinese Navy. Later, it appeared as the Luna for commercial sale, but did not have a very good reputation for quality. Improvements were made and the Western market was entered in 1985 with importation into the United States as the Astra III, and into Australia as the Alpha 40, while still carrying the GLH 130-40 nameplate.

In about 1986 the factory, by now named the Chan[g]zhou Marine Equipment Company, entered into an agreement for supply to Celestaire in the U.S., and, with improvements in quality, the instrument was marketed as the Astra IIIB. It is now also sold by Cassens and Plath as the CP Sailing sextant. The company now trades as a joint venture company Changzhou Celestaire Instrument Company. Since 2007 it has been producing the Astra III Professional, which has a bronze limb fused to an alloy frame.

It is not clear what the elements of the designation "GLH130-40" originally referred to. Current specsheets describing both the GLH130-40 (alloy limb, marketed in the US as "Astra IIIB") and the GLH 130-20 (bronze limb, marketed in the US as "Astra III Professional") imply that 40 and 20 refer to the specified instrument accuracy in arcseconds (+/- 20 for the GLH130-40; +/-10 for the GLH130-20). Specs given for the GLH130-60 state an accuracy of 60 arcseconds. The 130 probably refers to the measuring range of -5 to 130 degrees. It is less clear for what, if for anything, the letters GLH stand. In Chinese, these instruments are referred to as hanghai liufenyi 航海六分仪, meaning "nautical sextant.". It therefore seems possible that the L in GLH stands for liufenyi (sextant), while H might refer to hanghai (nautical). The G might refer to something like guochan 国产 "domestically produced" (as opposed to the C. Plath sextant on which it seems to be based), but this is pure speculation. Please note that the Chinese terms are given above in the Hanyu Pinyin romanization system, which was only developed in the 1950s. If the GLH designation indeed goes back to 1940 and if it is indeed an initialism based on some Chinese terms, the acronym would be based on another romanization system (Gwoyeu Romatzyh, the earlier official but rarely used standard being the obvious candidate). However, my impression is that roman-letter product designations, whether forming an initialism based on romanized Chinese words or not, became common only later in the People's Republic. If correct, this would suggest that the GLH designation came into use only later, even if production of GLH-type sextants already had started in 1940.

In 1940, Changzhou (located 150 kilometers northwest of Shanghai and close to the southern bank of the Yangtze river), like most of eastern (i. e., coastal) China, was occupied by the Japanese army. It is extremely unlikely that the Chinese national government, which had taken refuge in land-locked Sichuan, occupied itself with sextants. In any case, after the Japanese had destroyed whatever was left of the Chinese navy at the beginning of the Sino-Japanese war in 1937, there was no Chinese navy to speak of in the 1940s. If sextant production did indeed start in China in 1940, it must have been in occupied areas under Japanese orders, with the Japanese navy as the main recipient. Japanese involvement would go a long way in explaining how the C. Plath wartime design ended up in China. Before reading Bill Morris's book, I had suspected that the Chinese copied the SNO-M design during the time of Sino-Soviet cooperation in the 1950s, but Bill suggests that the C. Plath wartime design made its way into China and the Soviet Union independently.