Love those Mercians!
A couple things to ponder. Are you certain it is an '84, and not a '73? Funny thing with Mercian serial numbers is that sometimes the first two digits give the year, and sometimes it is the last two numbers that indicate the year. I'm pretty sure that even the folks at Mercian can't give definitive answers on this one as far as which way it was done for any particular year. However, the fact that there are bottle bosses would tend to indicate '84, as would the seat-stay plugs with the Mercian name in them (though even this bit of information doesn't make it definitive -- read on!). That "4" on the other side of the bottom bracket is actually a code to indicate the builder of your frame, not an indicator of the year.
As for model, it is either a King of Mercia, or possibly an "Olympic" model. Most KoMs have that heart cutout in the lugs (it's actually a little "pointy" to be a heart, isn't it?). The Olympic model has been discontinued, but it was still available in the 80s. I'm pretty sure that it was a pretty basic frame in the 80s, though I have seen some earlier ones with the heart cutout in the lugs.
Another thing about Mercians is that they are very much a custom order shop, and have been that way for a long time as far as I know. When it comes to braze-ons and other options, you might find that almost anything goes. You could find frames made in the same year, some with bottle braze-ons, some without -- some with downtube lever bosses, others without. Some with cable guide loops on the top tube, and others with slotted cable stops, others with no braze-ons at all. Details like the "Mercian" name engraved on the seat-stay plugs is open to preferences of the person ordering the frame -- even today, you can order a new Mercian either with that detail, or without it.
Check the History page on Mercian's website:
http://www.merciancycles.co.uk/
Kyle Brooks
Akron, OH
> [Original Message]
> From: Calvert Guthrie <prairieprinter@mac.com>
> To: <classicrendezvous@bikelist.org>
> Date: 7/9/2008 2:11:21 PM
> Subject: [CR]Mercian ID request
>
> I just snagged a black Mercian but can't nail down the model
> type from the info available online. The serial # is 7384 with
> a "4" on the opposite edge of the bracket---
> so we know it was built in '84 by "4".
>
> --Hearts had been cut out of the medium long point lugs.
> --Seat-stay plugs are pantoed, as is the Tange head set, with "MERCIAN".
> --Chrome chain side chain stay.
> --Top tube cable guide loops are filed very thin.
> --531c
> --Bottle bosses seat tube only.
> --Campy d/o's fender eyelets
>
> Could this be a "King of Mercia".
>
> Thanks.
>
> Calvert Guthrie
> Kansas City
> Missouri
> USA