Not listed in Rust [R],  nor Staunton [T].
The jazz label was started in September 1943 by William Miller of Melbourne and featured many well-known Australian artists. 
Period: 1943 to 1955. 
Size: Both 10 and 12 inch.
Series: The 10 inch ran from 1 to 36. The 12 inch ran from 1201-1206. There were also a few 10 inch re-issues from US sources that ran from R101 to R105. 
Material: All were issued on vinyl, except for S26 and S27 which are on shellac. 
Variety: The first two examples shown are very similar except that the position of the artist name and title are reversed. Adam Miller [A]also lists another label design with a characterature (of Roger Bell). There may be others. At least one album was on red vinyl (#32). 
 

This information gratefully received February 2011:
Hello Peter,
According to Johnson (Oxford Companion to Australian Jazz p. 213) William Henry ‘Bill’ Miller, in addition to founding the Ampersand label, “also started the XX label, specialising in reissues of ‘classic’ jazz.”. Hope this is helpful.
Ralph Powell

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Records in collection:

J12-01 sc3+ AMPERSAND
 Recorded Melbourne, 24 June 1947.
1201 (M55).  JUST A CLOSER WALK WITH THE. 
Graeme Bell's Dixdieland Band. Roger Bell, cornet. Ade Monsborough, trumpet, clarinet. Ian Pearce, trombone. Don Roberts, clarinet. Graeme Bell, piano. Jack Varney, banjo. Lou Silbereisen, bass. Russ Murphy, drums.
1201 (M53).  CREOLE BLUES.  Ibid.

J12-02 sc3+ AMPERSAND Ampersand Records, Melbourne.  Recorded Melbourne, 10 November 1945.
1204 (JR19/JR20). [a] GEORGIA CAMP MEETING [b] BACK HOME (Monsborough). The Bell-Monsborough Melbourne Jazzmen.  Roger Bell, cornet. Ade Monsborough, trumpet, clarinet. Peter Law, trombone. Don Roberts, clarinet. Graeme Bell, piano. Bub Baker, banjo. Jim Buchan, tuba. Russ Murphy, drums.
1204 (M54/M57). [a] I'M A LITTLE BLACKBIRD (Clark, Tuck, Meyer, Johnston) [b] ALEXANDER'S RAGTIME BAND.  Graeme Bell's Dixieland Band. Roger Bell, cornet. Ade Monsborough, trumpet, clarinet. Ian Pearce, trombone. Don Roberts, clarinet. Graeme Bell, piano. Jack Varney, banjo. Lou Silbereisen, bass. Russ Murphy, drums.

A003 c3 AMPERSAND Ampersand Records, Melbourne.  [Red vinyl]
32 (HW29).  HOBO SONG. Recorded Hobart, 3rd September 1950.  Tom Pickering's Good Time Music.
Col Wells, trumpet. Bennie Cubis, trombone. Tom Pickering, clarinet. Keith Stackhouse, piano. Geoff Sweeney, guitar. Ron Roberts, bass. Ced Pearcee, drums. 
32 (HW31).  RED HACKLE (Pickering). Ibid.

A005 c2 AMPERSAND  Ampersand Records, Melbourne. 
14 (M63).  TWO CLARINET BLUES  (Monsborough, Smith).  Recorded Melbourne, 28th June 1947. 
Lazy Ade's Back Room Jazz.  Ade Monsborough, clarinet. Kelly Smith, clarinet. Ian Pearce, trombone. Graeme Bell, piano. Russ Murphy, drums. 
14 (M62).  C 7th STOMP  (Monsborough).  Ibid. 

 A006 c3 AMPERSAND  Ampersand Records, Melbourne. 
33 (HW25).  NELLIE GRAY.  Recorded Hobart, mid 1950.  Col Wells & his Trio
Col Wells, trumpet. Keith Stckhouse, piano. Ced Pearce, drums. Tom Pickering, vocal.
33 (HW24).  BILL BAILEY  Recorded Hobart, mid 1950.  Tom Pickering Trio.  Ibid. 

A018 c3 AMPERSAND  Ampersand Records, Melbourne. 
12 (M47).  JUST A CLOSER WALK WITH THEE  (Trad. ).  Recorded Melbourne, 15th June 1947. 
Lazy Ade's Back Room Jazz.  Ade Monsborough, trumpet, clarinet, vocal. Kelly Smith, clarinet. Ian Pearce, trombone. Rex Green, piano. Jack Varney, banjo.
14 (M62).  IS THAT THE WAY? (Monsborough, Turner). Ibid.

Other artists included: Willie McIntyre's Jazz Band which included Tony Newstead on trumpet - and Don Reid on suitcase! Ted Herron's Jazzmanians - from Tasmania of course, recorded Launceston 1946. Jack Vanrney's Varmits with Ade Monsborough on clarinet, Frank Johnson's Dixielanders,Keith Hounslow's All Stars with the leader on cornet, Tom Pickering's Good Time Music, and  University Jazz Four.