Both auctions are offering the Patek Philippe ref. 3448, with Christie's example estimated to sell for CHF300 000-500 000 ($314 300-$523 850) whilst at Phillips the same model will be going under the hammer with an estimate of CHF200 000-300 000 ($209 535 -$314 300.)

Question is, why are two of the same watches being sold within 24 hours of each other estimated to bring in such drastically different prices?

Introduced in 1962, the reference 3448 was the first perpetual calendar from Patek Philippe with a self-winding movement. In the next 20 years that followed, only 586 examples of the watch were made, making them a must-have for collectors of the most rarest watches.

The watch was fitted with a new in-house caliber, the 27-460Q, which was patented by the firm.

And for all your hardcore watch fans, the 3448’s specifications are: 37.5 mm caliber Cal. 27-460 Q automatic, Geneva hallmark, moon phases, day and date display and perpetual calendar, 37 jewels, Gyromax balance, 18K gold wheel, matte silver dial, applied gold batons for squared figures, and auxiliary edges indicating the date and moon phases.

The production of the watch ended in 1981, the next model that was released after the 3448 was the Patek Philippe ref. 3450. These watches all featured a leap-year indicator.

Since 1989, examples of the 3448 have been offered at auction 189 times since, including every major case and dial configuration.

Particularly in the past 10 years, the popularity of the 3448 has skyrocketed.

Both examples being offered at Christie's and Phillips are in white gold, with only around 25 known to have been made in white gold.

First of all, the fact that the offering at Christie's is, what collectors will know is referred to as, a ''’full-set,'' as it is being sold in its original box, which in this instance has the original guarantee card stamped at Patek Philippe, Japan and dated 26th April, 1974.

Auction history proves that ‘’full-sets’’ fetch far higher prices in the sale room, on average, a boxed version can sell for £210 900 ($305 770) whilst the same un-boxed model with no papers, would sell for £114 440 ($165 920) on average in accordance to realised prices data.

The condition plays a pivotal role in determining its value. Among avid vintage watch collectors, you hear the word NOS (New Old Stock) pop up frequently, meaning the watch might be 25 years old, but never been worn, or is in pristine condition. To determine the condition, one of the quick checks is to inspect the watch lugs to see if they are even in thickness, the thicker/wider the lugs the better.

Previously, the highest average price achieved for a Patek Philippe 3448 was achieved at Christie's, proving that the auction house has the majority market share of that particular watch.

From 1989 to 2015, the 3448 has seen an incredible rise in success at auction. The white gold 3448 has been offered at auction 58 times, with 44 successfully being sold.

In the years 1989 to 1995, the average price paid at auction for a white gold 3448 was £39 033 ($56 590) which then rose to an average of £70 917 ($102 817) between the years of 1996 to 2000.

It has been in the 15 years that the growth in the market for this watch at auction has leapt, with the average price between 2006 to 2010 standing in at £220 200 ($319 250) with finally in the last five years the average auction price ringing in at £293 231($425 135.)

What is most fascinating, especially in terms of Christie's estimate, is that, on average, the 3448 has outperformed pre-sale estimates over the past 10 years. However, it is vital to note that on only two occasions, in 2008 and 2009, did the hammer price fall within the upper range of the pre-sale estimate, and not by a great deal.

In 2011, an 18k pink gold example sold at Christie's for a staggering $1.45 million, setting the record for the highest price paid for a 3448 at auction.

In 2013, a 3448 white gold sold for over a million. This was a very special watch as it had a leap-year indicator build in, unique to this piece.

The rare watch collecting market will be anticipating the final price paid for both watches. Firstly at Phillips, to see if the un-boxed version can trump these results and reach more than £293 000 ($424 800) secondly at Christie's, to see if the watch can blow all previous sales figures out of the water for the 3448 and bring in more than its top estimate of £360 415 ($522 540.)

All statistics and figures in this report has been collated by The Collectors Index, which monitors the market of fine wines, watches and classic cars to subscribers personal interests. See here for more information.

*Please note that all prices referred to are hammer prices and therefore exclude the buyer’s premium. Prices are reported in GBP (pounds sterling) at rates determined by the auction houses. Also note that historical results have not been adjusted for inflation.