How to identify the duplication

I’m working historical data.
it’s possible that the same person data in both 1850, 1860 and 1870 census.
Do you know how can i identity the duplication? Since there is no name or unique identifier available.

I see you’ve tagged this question under IPUMS International. Unfortunately, this sort of task is not possible with the data available in IPUMS International. This is possible using the complete count data available via IPUMS USA, in two different ways. First, we have pre-linked samples (available here). These files link individuals from the 1880 complete count file to 1% samples in 1850 to 1930. Second, you can perform these links yourself using the names of individuals. To gain access to the complete count census files with names, you’ll need to email with some brief information about yourself and your research project.

Thank you for your reply, and I want to ask if the complete count data available via IPUMS USA includes different countries or just USA?

The data available via IPUMS USA comes from the US decennial census and the American Community Survey (ACS). Therefore, it only includes data on residents of the United States.