"Should there be a duplicate entry, those ID's will be the same."
Without knowing whether this is a one-time thing or ongoing process, without knowing what these tables represent and without knowing why you have duplicate information, I can't really suggest the best approach. But no matter the reason, you will need to create a relationship between them in your graph as:
Table1:: ID = Table2:: ID
Then just place that 'special identifer' from table 2 directly on your layout from table 1. There is probably no need to duplicate it in Table1 (but I don't know why you have duplicate in two tables to begin with). If you really must place that special identifier in table 1, then you can easily do so after they are related (as described above). Some various approaches to consider:
1) Manually: You can place table1's special identifer field on a layout from Table 2. Show all records in table2. And then place your cursor in table1::special identifier and run Replace Field Contents (by calculation) and the calculation would be: table2::special identifier.
2) If this is regular process, don't place table 1's special identifier field on table 2's layout and instead script it:
Go To Layout [ layout based upon table 2 ]
Show All Records
Replace Field Contents [ without dialog calculated result ; Table1:: special identifier ; table2:: special identifier ]
3) After they are related, set Table1:: special identifier as auto-enter Lookup to table2:: special identifier then all future records will automatically look up the value. To bring the current records up to date, perform script :
Go To Layout [layout based upon table 1 ]
Show All Records (or only find records without special identifier value?)
Relookup Field Contents [ table1:: ID ] *
* keep in mind that this will relookup ALL of your fields in table 1 which have auto enter lookups.