Although TPM-2 is the latest weapon and now gradually entering service development is continuing of the TPM-1 though production has slowed dramatically because of the stockpile. TPM-1D4 is the latest version and will begin production later this month. 100 old TPM-1Bs will also be remanufactured to D4 standard.
D4 has modifications to the data link transponder to make the missile compatible with Dino data links (as TPM-2 already are), there are also improvements to the phasing field and storage security systems.
