These 10 locomotives were built by Plymouth in the USA and were used by the US Army in the south before 1975. According to the book "The Railways of Thailand", they were initially delivered to the Thai Railways (RSR) in 1963 (this appears to be correct) where they were apparently a bit of a failure. In Thailand they were numbered 2001-10. They were powered by two General Motors Detroit 12 cylinder, 2 stroke diesel engines each rated at a maximum of 475 hp at 2,100 rpm type 12V7 so a total of 950hp. Maximum tractive effort was 15,500 kg. They had a maximum speed of 80 kp/h though I doubt if there was any track in the south of Viet Nam at the time that would allow them to travel that fast! They weighed in at 52 tonnes in working order. Mr Raemar states that they stayed in Thailand for little more than a year and were then transferred to Southern Viet Nam where they were numbered 1988-97. This doesn't seem to be correct. Most sources give 1964 or 1963 as the year they were built and delivered to Thailand, and 1968 as the year they were transferred to Vietnam. (See different transfer date below) Later (after 1975?) they became the first D10H class and were numbered 31-40.

In Thai service they apparently had major problems with the high geared engines and transmissions.

In his book "The Railways of Thailand" R. Ramaer states that "all appear to have survived the Vietnam war" so were all still in service in 1975. He also states that "a few were seen derelict at Chi Hoa works early 1989". I'm presuming that unless evidence to the contrary is found, they would have all been scrapped by now.

Another  source states the following.

Built 1963 by Plymouth, USA.

Nos. 1988,89,90,91,92,93,94,95,96,97 were US army from Thailand in 1968. (not 1964 as listed in the Thai Railways Book)
They were apparently renumbered to 1001-10 at some time (1975?), though this numbering is not mentioned in Mr. Ramaer's book,
And renumbered again 31-40. Apparently only 31,34,36 and 38 actually carried these numbers. Does this mean the others had already been 'retired'? Also 1004, 06 and 10 were not carried. Again does this mean they were already removed from service?

The same source says they were all 'retired' by 1985.

Above: This scan was taken from a recent Vietnamese TV series. It shows BB1005 being repaired at Di An works alongside several BB907 (D9E) sometime after reunification in 1975. The photo raises a couple of questions.

First, when were the locomotives renumbered into the 'BB' numbering system and second, how long after reunfication did they retain these numbers? As the Northern system never appears to have used the 'BB' system, presumably before 1975. Were the locomotives absorbed into the southern system and renumbered after the US left in 1972, the previous numbers being US Army ones?

A third source, "Trains" magazine of April 1969 in an article by Je rry A. Pinkepank states that they were built in 1964 (should be 1963), that they were used by the Thai Railways until 1968 when they were sent to Saigon "to enter switching service in Saigon, relieving road units for use elsewhere". The road units being presumably BB901 and BB907 classes. The data in this article was supplied by Paul S. Stephanus, who I believe was serving in the US military in southern Vietnam at the time.

So they appear to have been built in 1963 and delivered to Vietnam some time in 1968 and were they purchased from the RSR (Thai State Railways) or were they always US military? Any help on this matter would be appreciated.

Tim Dolings's book also mentions these locomotives but mistakenly rates them as 400hp. As shown below they have two 475hp engines making them just under1000hp (hence D10H class). He suggest they were delivered sometime around 1968 (presumably from Thailand), and states that they were 'immediately set to work transporting rock and gravel for the construction of Tuy Hòa and Phù Cát airbases and various new road building programmes."  (page 158)

Bob Lehmuth has written from the USA and provided the following shipping dates from original Plymouth records:

Road Number	Shipped
31	12-6-1963
32	16-4-1963
33	22-4-1963
34	1-5-1963
35	26-4-1963
36	8-5-1963
37	20-5-1963
38	1-6-1963
39	8-6-1963
40	14-6-1963

He says they were shipped to Thailand via the US Army. So clearly they were built in 1963 not 1964.

All machines appear to have been scrapped.

Above: Diagram of Cr-8 as used in Thailand. Source: "The Railways of Thailand, by R. Ramaer.

Steam Locomotives generally used the traditional French classification system. A steam locomotive with a 2-8-2 wheel arrangement is classified as 141 class, a locomotive with  4-6-2 wheel arrangement is classified as 231 class etc. To differentiate between different locomotives with the same wheel arrangement, the initial road number was added, e.g. 231-400 and 231-500. Some northern locomotives of Chinese origin were also known by their Chinese classification. e.g. 141 also known as ZL.

Diesel locomotives have a completely dfferent clasification system.

All diesel classes start with the letter 'D'  (for diesel or possibly dau may for engine?) then a number which I believe is related to the locomotives  power output. The third character defines  Electric' (E) or hydraulic  (H).

e.g. D5H class = Diesel + 500 hp + hydraulic.

Before 1975 in the south  diesels used the French system , e.g. BB for  Bo-Bo type locomotive then the initial road number. e.g. BB901 class.

In the North there appears to have been a mixture of different systems.

There is also a semi-official system where locomotives are classified by their country of origin. e.g D5H is also known as 'Ừc' (Australian).