From SCM Microsystems:
Apple
For sale is a used SCR3310v2.0 USB smart card reader.The SCR3310v2.0 reads CAC cards and a variety of other smart cards. This unit is compatible with Windows XP/7/8 and MacOS.
Install Cac Card Reader On Mac
Update your SmartCardReader USB drivers for model SCR3310.SCM's SCR3310 and SCR3310v2.0 are small and ergonomic USB smart card readers, with backside mounting holes. The readers are ISO 7816 compliant, and can be used for cards in ID 1 card format.
This installer contains PC/SC driver and CT-API library and can be used for SCR531 USB, SCR331 CCID, SCR333, SCR335, SCR355, SCR338, SCR3310, SCR3311, SCR3320, SCR3340, @MAXX Family and SCT3511
Cac Card Reader For Mac 2018
SCR331 and SCR531 users note that only readers that have CCID firmware are supported. Readers that have firmware Rev 2.0 and above are CCID. This driver may also be used with the following third party products: Goldtouch ErgoSecure SC 2.0 keyboard, Datakey DKR830. If the host is running Windows 98 SE or Windows Me, ensure that Microsoft Smart Card Base Components are installed on the host before atempting to install the drivers.