The Lot Number is imprinted on the left tuck flap of the 500-round carton as indicated here.
The 1000-round intermediate carton does not have a Lot Number.

DO NOT USE WINCHESTER® M*22™ 22 Long Rifle RIMFIRE AMMUNITION WITH LOT NUMBERS GD42L or GD52L. Winchester has determined the above lots of 22 Long Rifle rimfire ammunition may contain double powder charges. Ammunition with double powder charges may subject the shooter or bystanders to a risk of serious personal injury and/or death, or cause firearm damage, rendering the firearm inoperable.

To determine if your ammunition is subject to this notice, review the Symbol Number and Lot Number. If it is Symbol Number S22LRT with a Lot Number GD42L or GD52L, immediately discontinue use. Contact Winchester toll-free at 866-423-5224 or visit Winchester’s Online Service Page to arrange free pick-up of the recalled ammunition.

This notice applies only to Symbol Number S22LRT with Lot Numbers GD42L and GD52L. Other Symbol Numbers or Lot Numbers are not subject to this recall. If you have any questions concerning this .22LR rimfire ammunition recall call Winchester toll-free 866-423-5224, or visit Winchester Customer Support online.