When you are looking at the MDCG-4 Series of Magnetic Reed switches from Littelfuse the portion of the part number after the series name is calling out the AT rating.
Applicable Part Numbers
HE574-ND HE503-ND HE655-ND HE652-ND HE653-ND F7864-ND F7865-ND F7863-ND HE656-ND F7866-ND F7867-ND HE654-ND MDCG-4-12-28-ND MDCG-4-17-38-ND MDCG-4-22-33-ND MDCG-4-27-38-ND MDCG-4-17-33-ND MDCG-4-7-18-ND MDCG-4-Q4067-ND
MDCG-4-12-18 MDCG-4-12-33 MDCG-4-27-33 MDCG-4-12-23 MDCG-4-17-23 MDCG-4-17-28 MDCG-4-22-38 MDCG-4-12-38 MDCG-4-32-38 MDCG-4-37-43 MDCG-4-7-13 MDCG-4-22-28 MDCG-4-12-28 MDCG-4-17-38 MDCG-4-22-33 MDCG-4-27-38 MDCG-4-17-33 MDCG-4-7-18 MDCG-4-Q4067