Correct -
I have a Model 1 - High Definition Graphics model - NON TMSS - which means it doesn't have the lockout chip Sega put it later revisions on the model. This one has a genuine YM2612 inside and probably the best filters.
My other Model 1 - does not say High Definition Graphics and has the TMSS lock out - so a "PRODUCED OR UNDER LICENSE FROM SEGA" splash screen appears first before game starts. Sound is still decent on this one - but I can't confirm it's AS good my top one.
This guide should help:
https://www.sega-16.com/forum/showthrea
m-bad-ones