Task: Data-Imputation (source dataset: WebTable)

Please fill in the missing value in the input table. The missing value is denoted by '[MISSING]'. Please only return the value filled in. Do not return the whole table.

No explanation, return the value filled in JSON format: {"value": "filled_value"}. 

Input Table:
| Date              | Mint mark   | Business strike mintage   | Proof mintage   |
|:------------------|:------------|:--------------------------|:----------------|
| 1964 (90% silver) | nan         | 273,304,004               | 3,950,762       |
| 1964 (90% silver) | D           | 156,205,446               | nan             |
| 1965 (40% silver) | nan         | 65,879,366                | nan             |
| 1966 (40% silver) | nan         | 108,984,932               | nan             |
| 1967 (40% silver) | [MISSING]   | 295,046,978               | nan             |
| 1968 (40% silver) | D           | 246,951,930               | nan             |
| 1968 (40% silver) | S           | nan                       | 3,041,506       |
| 1969 (40% silver) | D           | 129,881,800               | nan             |
| 1969 (40% silver) | S           | nan                       | 2,934,731       |
| 1970 (40% silver) | D           | 2,150,000                 | nan             |
| 1970 (40% silver) | S           | nan                       | 2,632,810       |
| 1971              | nan         | 155,164,000               | nan             |
| 1971              | D           | 302,097,424               | nan             |
| 1971              | S           | nan                       | 3,220,733       |
| 1972              | nan         | 153,180,000               | nan             |
| 1972              | D           | 141,890,000               | nan             |
| 1972              | S           | nan                       | 3,260,996       |
| 1973              | nan         | 64,964,000                | nan             |
| 1973              | D           | 83,171,400                | nan             |
| 1973              | S           | nan                       | 2,760,339       |
| 1974              | nan         | 201,596,000               | nan             |
| 1974              | D           | 79,066,300                | nan             |
| 1974              | S           | nan                       | 2,612,568       |
| 1976              | nan         | 234,308,000               | nan             |
| 1976              | D           | 287,565,248               | nan             |
| 1976              | S           | nan                       | 7,059,099       |
| 1976 (40% silver) | S           | 11,000,000                | nan             |
| 1976 (40% silver) | S           | nan                       | 4,000,000       |
| 1977              | nan         | 43,598,000                | nan             |
| 1977              | D           | 31,449,106                | nan             |
| 1977              | S           | nan                       | 3,251,152       |
| 1978              | nan         | 14,350,000                | nan             |
| 1978              | D           | 13,765,799                | nan             |
| 1978              | S           | nan                       | 3,127,781       |
| 1979              | nan         | 68,312,000                | nan             |
| 1979              | D           | 15,815,422                | nan             |
| 1979              | S           | nan                       | 3,677,175       |
| 1980              | P           | 44,134,000                | nan             |
| 1980              | D           | 33,456,449                | nan             |
| 1980              | S           | nan                       | 3,554,806       |
| 1981              | P           | 29,544,000                | nan             |
| 1981              | D           | 27,839,533                | nan             |
| 1981              | S           | nan                       | 4,063,083       |
| 1982              | P           | 10,819,000                | nan             |
| 1982              | D           | 13,140,102                | nan             |
| 1982              | S           | nan                       | 3,857,479       |
| 1983              | P           | 34,139,000                | nan             |
| 1983              | D           | 32,472,244                | nan             |
| 1983              | S           | nan                       | 3,279,126       |
| 1984              | P           | 26,029,000                | nan             |



row_idx: 4
col_idx: 1
col_name: Mint mark
label: nan