The accurate dating of bottles can be very difficult and often impossible. Few carry an actual date and on those that do, the date may just be the date that the company was established or when that particular design was first used. Usually the best that can be hoped for is a period when that particular type of bottle was used.
The well known Keiller marmalade pot is a good example of this. The company's first pots showed a wreath and the wording Keiller's Dundee Marmalade. In 1862 the company won a medal for their produce and added this to the printing. Another medal was won in 1873, this was again added to the pot. By the 1920s the shape of the jar had became thinner and taller, but these dates were still printed on it. Therefore the closest a Keiller pot can be dated is before 1862, between 1862 & 1873, between 1873 & 1920 and after 1920.
(Many of the Keillers advertised on the web as Victorian are actually after 1920)
The shape of a bottle, crudeness of manufacture, thickness of glass, shape of the lip or string rim, colouration and the type of mould used can all give clues to a period but this can only be gained through experience and handling bottles. Having personally dug thousands of bottles & pots from many accurately dated old rubbish dumps I am usually willing to have a stab at dating an item, but even with this background any estimate will only be a probability based on personal experience and could be wrong.
Numbers marked on stoneware are often only manufacturers batch or pattern numbers, even if they look like dates. Although this may sound rather negative, there are times when it is possible to give an actual date. The two figure number often found in the centre of the Bourne Denby potters stamp is accepted in Britain as being the date of manufacture. (e.g. 98 is 1898 and 02 is 1902).
Just occasionally mineral water and beer bottles do show the year of manufacture underneath, so it is always worth looking at the base. About 50% of flagons seem to have a date printed on them, so if you dig a piece of one from a dump check to see if this is on it as it can help tell when the dump was used and a likely date for any other finds from that site.
Sometimes pictures of today's collectable bottles appear in the advertisements in old magazines and these are an invaluable source of reference.- they not only show a period of use but also identify the contents of a particular type of bottle. (Bear in mind that standard shaped bottles were often used for a range of different products).
Researching through old trade journals in the library can show when a firm started trading, closed down or changed its trading name or address and help identify a period.
(e.g. John Gosnell & Co. who used a picture of the young Queen Victoria on its cherry toothpaste pots, became a Limited company in 1903. Therefore pots bearing Ltd must be after that date).
Today's problems with pirating & look-alike products are nothing new. It has long been common practice to cash in on popular products and a century ago competitors often packed their products in similar packaging, or gave it a similar name to a better know supplier.
(e.g. Bovril once had Bovil as a competitor).
From 1842 companies could protect their designs or trade marks by registering them with the Patents Office. Registration details were shown on the item and, although this will not give a bottle an actual date of manufacture, it will give the earliest date it could have been made and a likely period of use.
Between 1842 and 1883 this registration mark was in the form of a diamond (Registration Diamond) and from 1884 onward a number was used. At first sight the Registration diamond seems complicated to translate because of the code letters, but this is not so, it is surprisingly simple.
There are actually two diamonds, one type was used until 1860 and the other from 1861 to 1883. One the first, a letter is shown in the top of the diamond , in the later version a number is shown in the top. The reason being that the year was given a code letter and, once all the letters in the alphabet had been used, the year was then moved to the right hand side.
Both types of diamond used the same set of letters to show the month and a number showing the day of the month that the registration was made.
YEAR LETTER AT TOP
A 1845 G 1863 M 1859 S 1849 Y 1853
B 1858 H 1843 N 1864 T 1867 Z 1860
C 1844 I 1846 O 1862 U 1848
D 1852 J 1854 P 1851 V 1850
E 1855 K 1857 Q 1866 W 1865
F 1847 L 1856 R 1861 X 1842
YEAR LETTER ON RIGHT
A 1871 I 1872 U 1882
C 1870 J 1880 V 1876
D 1878 K 1873 W 1878
E 1881 L 1882 1-6th March
F 1873 P 1877 Y 1868
H 1869 S 1875 Z 1875
** CLASS - There are 13 classes, or types, of goods.
Those covering bottles are III glass & IV for ceramics
MONTH (Both Varieties)
Also December 1860
O Sometimes used for January
Also 1st - 19th September 1857
Once (most of ) the letters had been used a second time, the Patent Office quite sensibly changed the system to a straight forward register of numbers.
The numbers shown on the right was issued on January 1st of the year shown alongside. (January 2nd when the 1st fell on a Sunday) This is a much simpler system for identifying when a design was first registered.
E.g. 123456 would have been issued in 1889.
The number 1 was issued on 1st January 1884 for the Triangle Trademark used by Bass Brewery.
The registration number can be shown with a wide variety of prefixes such as: Registration Number; Reg; R.D.; Reg. Design; R.A.N.; Reg. No.
Most reference books only show registration numbers up to 1910, I have also added those for 1920, 1930, 1940 & 1950