| Heading and notes: | Form number E.T. No. 10. Standard Commonwealth interim format. Boxed message area and large area in centre for address. | 
| Message area: | 30 boxes in 6 lines. | 
| Reverse side: | Blank. | 
| Colours (text & form): | Black on light green paper. | 
| Size of form overall: | 141 × 218 mm. | 
| Size of datestamp box: | 35 × 33 mm. | 
|  | SI-RO-1. Adelaide to Lobethal Message ends with "Reply Paid". | 
Details of use and rarity.
| Form sub-number | Schedule number | Earliest recorded date | Rarity rating | 
| RO-1 | 12 March 1909 at Lobenthal. | RR |