The first Duophone record where produced by Vocalion and were pressed from the same masters used on their other labels such as Aco, Guardsman, Beltona, etc. The catalogue for 10" records was in a B-5000 series, and the 12" ones in an A-100 series. Some of the 10" records were pressed from masters unique to Duophone and used the same matrix series as Aco, etc, but with a DC- prefix rather than the usual C- prefix. They also had a run-off groove. The series ran until the summer of 1926, and the catalogue numbers didn't reach D-5200.

In September 1926, the syndicate, now at a new address of 18, Savile Row, London W1. announced a new Duophone record. This was a revolutionary Unbreakable Record. Many collectors tend to treat them a bit of a joke because most of these records found nowadays are extremely brittle and fragile. However, it is my opinion that the materials used have perished with age and at the time they were issued, they were unbreakable, or as near as makes no difference. They were made of a core of bonded layered paper, coated with a thin layer of some sort of  rubberised plastic. An article (not an advert) in Melody Maker at the time of their launch gives the record a glowing report (click on thumbnail picture right to see full article), extracts of which are below this narrative. The records cost just 1/- (5p) and were in a UB-2001 series. All recording were British, acoustic and recorded specifically for Duophone. I believe the recordings were done by Vocalion, using their acoustic system, and continuing their acoustic matrices, only with a DU- prefix. The catalogue didn't get far, UB-2131 is the highest I know. The last few UB-series Duophone also appear with a red label  but with the same design as the purple ones. 

In 1927, Duophone re-launched their unbreakable records, with a smart (and bright) red label using an M-100 series catalogue number. Other catalogue series are also used, such as an  A-1 and C-1 series, often duplicating what is found on the M-100 series. The M- series are much more solid and generally survive in better condition that the UB- ones. There is still a  tendency for the surface to "craze", but I have a number that are fairly pristine and play well. English masters were still acoustic and, confusingly, use at least 3 sets of matrix numbers. Some have the DU- series - mainly items that had already been issued on the Purple label. Later items have an MO-5000 series and/or a PB-1 series (often both on the same record!).  American matrices were also available on the M-series. These were from Emerson and were Electrically recorded, albeit with a rather thin sound. Some items may be found with either a British matrix or an American one; presumably the American master wore out or got damaged and a British one had to be substituted? Many were issued as "Savile Dance Orchestra" - named after their address. The catalogue series may not have reached M-200; the highest I have is M-171.

In August 1928, the Duophone and Unbreakable Record Co Ltd, as it was now known, gained control of British Brunswick Ltd, and moved once again, to 15-19, Cavendish Place, London W1. They made a number of recordings during this period, but few were ever released; though test pressings exist of some of them. There are electrically recorded items by Stan Greening's band  and Pete Mandell's band with DU-100 catalogue numbers and using an FB- and DB-series matrix range. Also at least one 8" test, with a label similar to that on the next series...

In 1929, Duophone started issuing their new records, still in the "Unbreakable" style, with a sober brown and gold label and a D-4000 series. The vast majority of the records were recorded by Brunswick in America, many not issued in their homeland.  The series made it up to about D-4060 before the money ran out. Many of the D-4000 series were also issued on a Purple "normal shellac" records as well. I understand these were actually re-issues, as these don't actually reach as far as the last issues on the unbreakable version. The financial situation was pretty bad by the Autumn of 1929  (and not just for Duophone), but as a final gasp, they started an F-2000 series, using British matrices in a DFR-1 (later just DF-) series. The records were unbreakable an used the same label style as the D-4000 series. There was also a D-500 series issuing more serious music. 

Duophones: Are they really unbreakable????

The following are extracts from an article in the Melody Maker at the time of the launch of the UB-series, plus my comments (in red). Remember this wasn't an advert, but an impartial article. The full article may be read by clicking on the thumbnail picture above right (below the 2nd label picture).

"As a first demonstration we were invited to listen to two records pressed from the same master. The first was the ordinary well-known Duophone heavy type of disc (i.e. a shellac one). The second was an early sample of the new indestructible type. It could be rolled up into a small tube without damage. Hardly any difference was noticable in the reproduction, except that the indestructible record was conspicuous for considerable less surface scratch than the other."

It seems incredible that they were ever flexible enough to roll into a tube, but some of the records are extremely thin, and if the groove coating was rubbery enough, it could well have been that flexible, rather like a Durium.

"A further advantage as regards wear was demonstrated by scratching the recording surface with a knife. This severe treatment had no effect on the reproduction, until such a deep and forceful incision had been made that it penetrated the inner core."

I find this difficult to believe, unless the surface was such that a scratch with a knife just had no effect on the surface, rather like the "cutting mats" that you can get nowadays, for craft work. (mmm.. that's a thought)

"We noticed that an ordinary needle could only serve for one tune, it then being entirely worn out. We were assured that this did not affect the record itself, this being merely proof of its wearing power and it could be played a greater aggregate of times than the ordinary shellac record, without reproduction being impaired."

If you played one with a steel needle today, it just rips the surface right off. Surely this proves the surface has in fact perished in the 70-odd years since production.