Engelhard 4oz Silver Bar -- Have One And Wish To Sell It. Advice?

I have such a bar that's been in my possession for many years. I acquired it by chance from a former roommate and it's been sitting in a knick-knack drawer for decades. I'm not a bullion collector and learned only a few years ago that it was particularly collectible. I've just registered at this site today.

The site owner at allengelhard.com was made aware of this bar when he was starting his site. I think he's added its serial number to his database. This bar reads 'Engelhard' in an elongated octagon with the lines below reading '4.000' and '999' (the 999 appearing without a '+' symbol as others have) and a five-digit serial number in the two-hundreds range. I can provide pictures... should I obscure the serial number for safety purposes? I can also post pics with additions to the picture for validation purposes as long as they're reasonable requests. :-)

Since I have never sold anything on ebay, or even know if that's the right place to sell it, I was wondering what advice this forum might give to a first-time seller who is not an expert in nor collector of what I have in my possession. I'd like people who are genuine collectors of Engelhard bars seeking a 4oz to their collection the best chance to know it's available to acquire. All I know is that I'd have to insist on a USPS money order for domestic US sales or a wire transfer for collectors outside the USA. I also have a preference for sending the bar via 'US Postal Service Registered Mail, Insured' for the agreed price of the bar. I don't think I'd ship anything expensive or unique in any other way.

Note: I did just a few moments ago offer it to a collector who wrote a post from 2013 that they were seeking exactly this species of silver bar and I'm awaiting their reply. So far, the email hasn't bounced back. Out of courtesy I'd like to give them a chance to respond.

I hope I'm not breaking any forum rules. Thanks for reading, all.