how can you tell a real grete jalk coffee table from a replica?  

Real
If the table has the same dimensions, details, and quality as a documented Grete Jalk design, and it has the Glostrup label, it?s more than likely real. I?ve never seen a knockoff. Jalk tables are not all that uncommon.

I've seen a knock off...
I had a Grete Jalk coffee table and I've also seen a knock off.....it was very close, though the fins were not quite as nicely executed. The dead giveaway was the copy had Robertson screws. Robertson screws never made it to Europe from what I understand. Also, the Jalk has the slightest splay to the legs, the knock off does not.
Hope that helps...

Are there knock-offs of the...
Are there knock-offs of the Grete Jalk coffee tables?
No, there is not.
Her design was actually a pretty common one.
There were MANY furniture manufacturers making similar styled tables, but they are not copies or knockoffs.
If yours has a label, its real.

I stand corrected....Perhaps...
I stand corrected....Perhaps I misspoke using the word knock off....how about eerily similar? I have seen a table so close to the Grete Jalk surely one could be forgiven in thinking it was copied deliberately to capitalize on the teak madness of the 60's /70?. But I digress... I think her table had enough razzamatazz going on to set it apart from some others...

Here is one you
can compare with.
Glostrup tables alayws have the lip turned down under where the Original P Jeppesen has the lip turned up.

thanks for all of your...
thanks for all of your responses. if the design was not uncommon, why are they selling for as high as $1600?
also, the table i found for around $600 has a different glostrup label (silver, black, and red) than the one shown in the previous post, but the lip of the table is turned up. is the glostrup always made with lip turned down?

Glostrup with upturned lip
...
http://www.deconet.com/product/290969/Fine_danish_Sofa_/_Coffee_Table_in...

Does the lip up /down apply...
Does the lip up /down apply to her side table as well? I have one of her side tables with the Glostrup label and the lip is upturned...I don't recall ever seeing one with the lip downward before...

1600$
seems a lot, although I very much apreciate the design and vision of grete.
Here they tend to go for 200-800? (central europe).

http://www.ebay.com/itm/Rare-?...http://www.ebay.com/itm/Rare-Rosewood-Mid-Century-Modern-Danish-Coffee-T...
if you look at this ebay listing (not the same listing that i was looking at), the table shown has a glostrup sticker, but it is shorter at 51 inches. Most of the tables I've seen are around 63 inches. Also, there are fewer slats on the lower shelf. Is this fake?

My dearest fellow poster rockone....,
Please learn the usage of the associated web link box below. It make it much easier for a lazy "booze hag" like me to keep up.
ps. what a sweet table. and keep posting!
Best to all,

Well designed
Danish stuff tends to go for a premium in the US.
Even the generic stuff does quite well.

Same in Canada woodywood...
I bought my Grete Jalk coffee table at a garage sale a few years for $45.A lucky find. Of course, dazzled by all that sheeny teak I would have paid twice that...
Even thrift stores and my local GW have caught on in the last year, low quality generic stuff in fair condition is way overpriced. Even items that have the slightest hint of anything Danishy are priced quite high....
To the OP....I believe these tables came in 2 sizes...the shorter one has seven slats, the longer one has 9...

Conversely here in Canada
The explosion of mid-mod shops in some places has increased the competition and helped to keep the prices down, but you will still see extremes. I sold one of these at a show last year for a mere 350, and on Queen St. in Toronto I've seen them for only 450.