The Tachy ring is usually white, rather than the matching blue of this example.

One of our fellow collectors over on Vetroplastica has been able to confirm that the case is marked 1153, but the first two numbers of the serial aren't legible.

I've collected quite a few photos together now, but have no serial number information. So if anyone out there has one of these, it would be really useful if you could let me know the first three digits of the serial number so we have a better idea of the timescale for them. Any further photos are welcome too, particularly if you have any of a variant with red markings rather than orange and with different markers... which might be a story for another day!

Thanks in advance, Mark