The year and month started to be used at this point after 1956, so the change code is not really necessary in newer tubes to pinpoint a manufacture date.

年份和月份开始将在1956年后使用这一点，所以更改代码是不是真的有必要在新管查明制造日期。

youdao

If you can provide the 3-4 digit alpha-numeric code located on the bottom of the packaging, this will allow us to determine the date of manufacture.

如果你能提供3- 4位数的字母，数字代号，位于底部的包装，这将使我们能够确定生产日期。

youdao

If you can provide the 3-4 digit alpha-numeric code located on the bottom of the packaging, this will allow us to determine the date of manufacture.

如果你能提供3- 4位数的字母，数字代号，位于底部的包装，这将使我们能够确定生产日期。

youdao