| Number | Date | Country | Kind |
|---|---|---|---|
| 54/100593 | Aug 1979 | JPX |
| Number | Name | Date | Kind |
|---|---|---|---|
| 2592368 | Yackel | Apr 1952 | |
| 2685510 | Yackel | Aug 1954 | |
| 2751295 | Salminen et al. | Jun 1956 | |
| 2856283 | Yackel et al. | Oct 1958 | |
| 3143414 | Yackel et al. | Aug 1964 | |
| 3440049 | Moede | Apr 1969 | |
| 3639126 | Verelst | Feb 1972 |
| Entry |
|---|
| Pontius, Photographic Science and Technique, PSA Journal, Section B, Sep. 1951, pp. 76-79. |