RFCs 3925 and 2131 (https://tools.ietf.org/html/rfc2131) (https://tools.ietf.org/html/rfc3925)
Allow for the use of DHCP clients to send client option 60 to identify the equipment or vendor type, and for the DHCP server to send different vendor specific information in option 43 back to clients based on how they identified themselves using dchp client option 60.
One practical example of this is that both Ubiquiti Unifi access points and Cambium cnPilot access points require the use of DHCP option 43 to direct them to their wireless controller. Since the two require different controllers - in order to deploy a mix of Cambium and Ubiquiti access points in the same network segment would require the mikrotik DHCP server to send one value for option 43 to the ubiquiti devices, and a different value for option 43 to the cambium devices (as identified by DHCP client option 60).
This scenario does not seem to be currently supported.
This scenario has been discussed here http://forum.mikrotik.com/t/dhcp-server-option-43-vendor-specific-based-on-clients-dhcp-option-60/85642/1 with hacky workarounds.
It is now possible for Mikrotik DHCP clients to send client option 60: http://forum.mikrotik.com/t/dhcp-client-option-60/42472/1 but it doesn’t seem possible for Mikrotik DHCP server to act on this option.
Note that this feature request is different from http://forum.mikrotik.com/t/feature-request-add-support-for-rfc-3925/55078/1 as that requests support in the Mikrotik DHCP client, not server.