If I am understanding your question correctly, you don't have Manufacturer Model or Catalog numbers and want to avoid having duplicates of the same part in ITEM MASTER / INVENTORY.
The only way I believe you could accomplish this would be to make your ITEM # the OEM Catalog information, which I would not recommend doing. If the OEM changes their Catalog #, you would need to OBSOLETE the ITEM and create a new ITEM with the updated part number.
We have over 8,000 records in our INVENTORY and we use CATALOG # as the primary field for entering the OEM part information which we can quickly do a search from the GUI of Maximo without having to download to Excel / Access to create filters to look for duplicates.
This also helps with INVENTORY REORDER so if you set that up for the site, you have all the information already configured so when you issue a PR / PO to the vendor, the OEM part number or vendor part number is on the PO for them to fulfill your order.
Regards,
Chad