The French Colonial Administration of French Indochina (today Vietnam) ordered five locomotives for their rack railway the Chemin de fer de l'Indochine (CFI) which operated between Song Pha and Da Lat.
 
The first locomotive was number 701 built in 1923 by Schweizerische Lokomotiv und Maschinenfabrik (SLM) of Winterthur, Switzerland.
 
The engine was based on the HG 4/5 rack and pinion design of 1914 constructed for the Nilgiri Railway in India.
 
However, this newer HG 4/4 version's power output was significantly increased.
 
In 1929 a factory at Esslingen in Germany supplied two more (706 and 707) of these locomotives built under license from SLM as war indemnification.
 
Two additional engines were built by SLM in 1930 (708 and 709) for a total of nine constructed.
 
Locomotives 701, 705, 707, and 709 were destroyed in World War II during the Japanese occupation of Indochina.
 
Locomotive number 702 was reported damaged and apparently located at Cau Dat, Vietnam.
 
There are at least two Cau Dat's, one in Da Lat and another in Haiphong, and there's no confirmation it's at either location.
 
The disposition of number 703 is unknown.
 
Later, in 1949, the remaining locomotives received new numbers with the prefix VHX (Vietnam Hoa Xa) under a Vietnamese administration.
 
The railway was severely damaged during the Vietnam War and all locomotives, including the HG 3/4 types, fell into disrepair and rust.
 
(HG 3/4 numbers 1, 2, 8, ad 9 were repatriated to Switzerland, but that's another story.)
 
Then in 1983, after several years of negotiations, a Swiss group purchased and repatriated two HG 4/4 engines.
 
In 1990 numbers 704 and 708 were shipped to the Dampfbahn Furka-Bergstrecke (DFB) workshop in Chur, Switzerland, with 706 following in 1997 to be used for spare parts.
 
First to be rebuilt was number 704 taking 12 years and 48,000 hours of volunteer labour.
 
The official unveiling occurred at the Uzwil workshop on 15 Jun 2018 after which it was transported by low-boy to the Museum of Transport at Lucerne for a 3 day display and event, then onto Realp.
 
On 5 Jul 2018 HG 4/4 number 704 was fired up at Realp for its first test run on DFB trackage.
 
William Slim.