USSR
Text: "The world's first radio-set (lightning detector) by A.S. Popov (1895)"
| Country: | USSR |
| Type: | Postage stamps |
| Series: | Radio Day |
| Nominal: | 40 k |
| Year: | 1949 |
| Size: | 26 x 37 mm |
| Perforation: | line 12½ |
| Mintage: | 1,000,000 |
