I think his intent on using consignment is to:
1.) Reach a larger market.
2.) Not have to deal with asking about it.
I would suggest trying to sell it here in the
NFA EE. You can specify an in-state buyer only (no need for a dealer to transfer it) or even deal with out of state shipping if you want. Shipping out of state would be very unlikely unless you had a ridiculously low price, since $400 in transfer taxes would be involved.
For example:
New HALOs have an MSRP of $675 + $200 = $875. If you sell it in-state, you could probably get $550 for it, and the buyer would be into it for $750. If you try and sell it out of state, the buyer would be looking at $400 in taxes, which means he wouldn't buy your suppressor for any more than $350. That means his total outlay is $750. If you tried to sell it out of state for $550, it would cost more than having the buyer order one through an in-state dealer and save the extra $200 transfer tax. Follow?