@saulh
Hi and best compliments for the turntable;
the armboard above you can use it for the following vintage and contemporary tonearms to the turntable
Stax UA-7, UA-70, Fidelity Research FR-64, FR-64S, Saec WE-308, WE-308L, Ortofon RMG212, RMG309, Micro Seiki MA-505, MA-505L Grace G-704 G714
The lower armboard would appear to be compatible with the SME 3009 arms etc. but you don’t see 4 small holes around the main hole.