The labels on the antibody vials show a lot number consisting of the article number and one or two more digits e.g., "Lot 104211/15" or just "Lot 15".
These lot numbers distinguish different batches of lyophilization and are for internal control only.
Since 2017 the prefix 1-, 2-, 3- etc. is added to the lot number. This prefix changes if the new lot comes from a different immunization. New lots of polyclonals from the same immunization as before all have an identical prefix. Monoclonals always carry the prefix 1- since they always originate from the same clone. E.g. "Lot 104211/1-15" or "Lot 1-15".
When the lyophilized stock material of a product is running low, a new batch (10-50 units depending on the frequency of sale) will be lyophilized. One unit of each new batch is taken for testing and only if tested positive that batch will be stocked for sale.
It comes on sale when the previous lot is sold out. Due to this schedule, all products are always on stock and ready for sale.
Hence, it is not possible to choose among different lots. Buying the same lot again is only possible if that lot is not yet out of stock.