Dating your Wal...
If you happen to own a Custom Series Bass your job is very, very simple... Just take the control cavity plate off the back off your bass and you should find a small piece of masking tape with all the info you need (and more) written on it!
One point to make about this... The masking tape is written by whoever happened to give the bass it's final check and once-over. Several basses have been listed on eBay stating "Made by Ian Waller himself and signed inside..." as if this means that it should command a higher price for its rarity. This is not the case. All Wals will have been worked on by whoever was working in the Electric Wood workshops in that period. Therefore ALL Wal basses built before Ian Waller died will have been extensively worked on by him - while it's nice to think that the signature on your bass is Ian's no such basses ought to command an elevated price just for the presence of his signature.
Pro series and other Wals are a little more difficult.
However, numerically the numbering of Wals is broadly sequential - starting from W1111.
The JG series followed on with a JG prefix replacing the W - JG1111. According to Electric Wood records only 44 JGs were ever made (JP1111, JG1111 - JG1153) - they also give details on 36 of the original owners.
The first JG went to Wal stalwart John G Perry but had a serial number JP1111. The next, JG1111 was a demo model which went to Trident Studios off Wardour Street, London. John Gustafson's fretted JG was next, JG1112 - he later returned for a fretless, JG1131. The last JG was JG1153 (which it seems was retrofitted in 1981 with a Pro IIE scratchplate).
With the introduction of the Pro series basses the JG changed to PB and the numbering reverted to 1111 (again). The first two Pro Basses (PB1111 and PB1112 were kept by Wal, the following few being shipped off to Barret's in Manchester - this was March 1979. These early Pros had plain headstocks. From May 1979 the Pros had the more usual striped headstocks. This change back to PB1111 explains a degree of confusion in the numbering of Wals in this transitional period... a PB1131 exists but then, so does JG1139! The Pro Series ran from 1979 to 1982 when the new Custom Series Basses were introduced. The last ever PB numbered bass being PB1859 (although this to all intents and purposes was a Custom Series bass) - subsequent basses returned to a W prefix - W1860 one would presume!
All remained calm on the numbering front until around 1996 when a new numbering system was introduced. This retained the W prefix but gave the date on which the bass was completed. Under this system W30496 would be dated 30 April 1994, W7899 would be 7 August 1999 and W28601 would be 28 June 2001 - American cousins take note of the British date convention! Just to confuse matters all through this period some basses were still being numbered sequentially at the request of customers who preferred the old fashioned way of dating a Wal!
One thing you can be sure of is that there are enough anomalies in there to keep the Wal dating game interesting and surprising! In the end your best bet may be to visit the now somewhat defunct Wal databse compiled some years ago by Stephan Koester's. Although not updated fro some time it is reproduced here... You may find a number near the number of your bass and see what date that one was built! Yours will be close to that date... probably!